How about the given-animal-traits trope but it's Kacchan being turned half-cat and everyone is like "awww cute baby give him all the pats" but Kacchan got exclusively the traits where he pushes shit off tables, takes people's seats the moment they get up, and takes over your bed

Deku, getting back to his dorm after a long day: Kacchan what are you doing here? I'm about to go to bed
Kacchan, curled up on Deku's pillow: Ignores him
Deku: Kacchan please move I'm exhausted
Kacchan: flicks tail and silently glares

Deku: sighs and crawls into the sliver of space beside Kacchan to get some sleep
Kacchan: yawns and drapes himself over Deku's face
Deku: Okay Kacchan I love you too goodnight

Deku, waking up at 5am to a loud crash: WH- HAH- WHO- Oh, Kacchan, it's you
Kacchan, holding a threatening paw to Deku's favourite All Might figure: Feed me
Deku: Can't you get your own food
Kacchan: I SAID FEED ME

Kacchan: Deku, rub my tummy
Deku, hands covered in fresh cuts: I'm not falling for that again, Kacchan.
Kacchan, pouting and acting cute: Please Deku, I want the tummy rubs
Deku, sighing: Okay but you better not- OW, KACCHAN, YOU DICK THAT HURTS
Kacchan: Deku, rub my tummy again

Kacchan: Deku open this damn door right now
Deku: Kacchan I'm getting changed
Kacchan: OPEN IT
Deku: Okay, okay!
*Opens door*
Kacchan: Turns and walks away

Deku, closing the door: I should have known
Kacchan: OPEN THAT DAMN DOOR, DEKU
Deku: YOU DIDN'T EVEN COME IN
Kacchan: OPEN IT
Deku: Sighs and opens the door

Kacchan: Walks into the room
Deku, sighing: Okay are you happy now?
*closes the door behind him*
Kacchan: Open the door
Deku: But you're already in here
Kacchan: I SAID OPEN THE DOOR I NEED TO KNOW WHAT'S ON THE OTHER SIDE
Deku: YOU JUST CAME FROM THERE
Kacchan: OPEN IT

Kacchan, coming in soaking wet from outside: Deku it's raining and I'm cold
Deku: Oh hold on let me get you a towel
Kacchan, dropping into Deku's lap: I'm cold, make it stop raining
Deku: I can't get a towel if you're sitting on me
Kacchan: Make it stop

Kacchan: I'm going outside
Deku: You just got dry, it's still raining
Kacchan: It might not be raining out the other door
Deku: It is definitely raining out the other door
Kacchan: But it might not be
Deku: It is.
Kacchan: I have to know.

Kacchan, once again drenched: Deku it's raining out there too
Deku: I told you it was
Kacchan: Why didn't you make it stop
Deku: ...
Kacchan: Now I'm cold and wet
Deku, sighing: I'll go get another towel

Kacchan: Sits down beside Deku, purring
Deku: Awww aren't you affectionate today?
Kacchan: lies across Deku's laptop keyboard, still purring
Deku: Kacchan I'm meant to be doing my homework, can you move a little so I can have my computer back?
Kacchan: No

Kacchan: Pat me
Deku: I am patting you
Kacchan: Both hands
Deku: You don't need both hands
Kacchan: BOTH HANDS
Deku: Sighs and pats him with both hands

Kacchan: Deku
Deku: Yes Kacchan?
Kacchan: Deku
Deku: What, Kacchan
Kacchan: Deku
Deku, looking up: Are you sitting in a cardboard box?
Kacchan: Deku I found a box

Kirishima: Hey Midoriya! You look tired, are you oka- Um, what's that string for?
Deku: Twitches string
Kacchan: Dives on string like it's the most fearsome villain in the world, quirk popping as he rolls around clutching it
Kirishima: You... Have fun with that, man.

Kacchan, pushing things off Deku's school desk: Move this I don't like it
Deku: Kacchan please Aizawa is talking
Kacchan: Move it
Deku: Sighs and moves his textbook over
Kacchan, climbing up to sit on Deku's desk: My spot

Kacchan: Rolls around on the rug in the dorm's common room
Deku: What are you doing on the floor
Kacchan: Rolling
Deku: Why?
Kacchan: Rug
Deku: Is the rug... comfortable...?
Kacchan: Can't talk, rolling
Deku: I... Kind of want to try this...

Uraraka, walking in on both boys rolling around on the carpet: You know what I'll come back later

Kacchan: Scratches at Deku's door in the middle of the night, whining
Deku: What do you want, Kacchan
Kacchan: Let me innnnn
Deku: It's unlocked, let yourself in
Kacchan: Let me innnnn
Deku: Sighs and gets out of bed

Kacchan: I'm sleeping here
Deku: Oh, again? Okay, sure
Kacchan: Sits on Deku's pillow
Deku: NO, NOT AGAIN
Kacchan: Too late, fucker, this is my spot
Deku: God damn it

Deku: Have you seen my phone? I can't find it
Kacchan: Nope
Deku: Are you sure? I've looked everywhere
Kacchan: No clue
Deku: Can I borrow yours to call it?
Kacchan: Knock yourself out
Deku: Calls his phone and hears it clearly ring under Kacchan's ass
Kacchan: Haven't seen it

Kacchan: Deku, feed me
Deku: You just had lunch
Kacchan: I'm still hungry
Deku: Get a snack, you're still mostly human
Kacchan: Deku
Deku: I'm not making you food
Kacchan: Deku
Deku: No
Kacchan: Deku
Deku, exasperated: What?
Kacchan: Feed me

Kaminari: Walks past
Kacchan: YOU PIECE OF SHIT CUT IT OUT
Kaminari: What?! What did I do?!
Deku: You blocked his sunny spot
Kaminari: Slowly takes a step sideways, away from the window
Kacchan: Lies back down, sighing contentedly, and immediately goes back to sleep in the sun

Deku: Hears thumps from Kacchan's room and barges in to check on him
Kacchan: Spinning frantically round and round in circles
Deku: What's wrong Kacchan?!
Kacchan: Gotta catch it
Deku: Gotta catch... Are you chasing your tail?
Kacchan: GOTTA CATCH IT

Kacchan: Wandering around the classroom aimlessly while teachers are talking and people are working
Aizawa: Bakugou please return to your seat
Kacchan: Rubs against his legs and purrs
Aizawa: Okay nvm class dismissed

Uraraka: Deku-kun would you like to come out to lunch with us?
Deku: I would love to but I can't get up
Uraraka, staring at Katsuki asleep in Deku's lap: Can't you just... move him...?
Deku, tearing up: How dare you he's so comfy

Kacchan, sitting at Deku's dorm room door: Deku I brought you a present
Deku: Oh God Kacchan no please don't start bringing me dead mice
Kacchan: It's a present
Deku: Oh God Kacchan why
Kacchan: Come look, do you like it?
Deku: Is this... Katsudon?
Kacchan: I killed it for you

Deku, sitting on the couch eating dinner: Do you need something, Kacchan?
Kacchan, perched on the armrest beside him, staring at him unnervingly: What are you eating
Deku, sighing: Do you want to try some of my dinner, Kacchan?
Kacchan: Gimme

Kacchan: Sprints full-speed down the street, hissing.
Deku: Oh shit is there a vill-
Random dog, chasing Kacchan gleefully: Arf!

Kacchan: Crouches on the floor, staring into the hallway
Footsteps
Kacchan: Wiggles his butt
Louder footsteps
Kacchan: Tackles Deku to the ground as he passes, amidst squeals of "Kacchan no! Bad Kacchan!"

Deku: Walks in the door with hands full of groceries
Kacchan: WHERE WERE YOU
Deku: The- The grocery store?
Kacchan: I THOUGHT YOU WEREN'T COMING BACK
Deku: Aww, were you worried?
Kacchan: TCH, NO, OF COURSE NOT, LEAVE ME ALONE
Also Kacchan: sticks close to Deku's feet all night

Kacchan: draped across Deku in bed, happily snoring/purring as he snoozes
Deku: Stroking his hair, marvelling at how soft and warm he is and how he's getting away with the petting
Kacchan: Stretches, shoving his butt right in Deku's face

Kacchan: licking his wounds after training
Deku: Kacchan that's gross, come use the shower
Kacchan: You can't fool me, nerd, the shower is WET
Deku: Well can you at least not attempt to lick your crotch in the middle of the common room?

[Side note: I think this is the most likes I've ever gotten on a tweet/thread. I'm glad you like Katsukitty as much as I do!]

Kacchan: Sits on the couch
Kacchan: Moves to the floor
Kacchan: Gets on Deku's lap
Kacchan: Moves back to the couch
Deku: Kacchan please just make up your mind
Kacchan: What the hell are you talking about?

Kacchan: Where did it go?
Kaminari: Giggling
Kacchan: WHERE DID IT GO?
Kaminari: Turns on the laser pointer
Kacchan: THERE IT IS. WHAT THE FUCK IS IT. I WANT IT.

Kirishima, opening the door: Hey bro, do you mind if I borrow... your...?
Kacchan, curled up on his bed gnawing on an old All Might plushie: Say a word and you die
Kirishima: I saw nothing
Kacchan: Take the notes and go
Deku, in the distance: Has anyone seen my All Might plushie?

When Kacchan finds out he is outraged, threatening to kill Kaminari for his games. He is promptly distracted from his anger when that stupid red dot shows up again. Seriously, where the fuck is it coming from?! https://twitter.com/shosdaddyissues/status/1302549482425528321

Saturday night is Bakusquad movie night. They each submit what they want to watch into a hat, to be drawn at random.
Mina: Mean Girls
Kaminari: Die Hard
Kirishima: The Karate Kid
Sero: A Clockwork Orange
Kacchan: Videos for cats to watch - 8 hour bird bonanza

[I'm going to bed now but maybe I'll come up with some more tomorrow when my cats start being a pain again]

Deku: Walking to the bathroom early in the morning
Kacchan: Where are you going I'm coming too
Deku: I'll be right back Kacchan, just wait there
Kacchan: I'm coming with you
Deku: I just need to pee
Kacchan: I'll come too
Deku, sighing as Kacchan follows him into the toilet: fine

Deku: At least look the other way while I pee
Kacchan: Pat me
Deku: In a minute
Kacchan: Pat me NOW
Deku: Kacchan I'm-
Kacchan: DEKU. PAT.
Deku: Okay, okay! Here, pats
Kacchan: Both hands
Deku: N O

Kacchan: I want to look out the window
Deku: You have legs, stand up and look
Kacchan: Pick me up so I can look out the window
Deku: Just stand up!!
Kacchan: I WANT TO LOOK OUT THE DAMN WINDOW, DEKU, PICK ME UP SO I CAN SEE
Deku, sighing as he lifts Kacchan up: Am I too nice?

Deku, brushing Kacchan's hair: Do you always shed this much or is this a cat thing? You're gonna go bald at this rate
Kacchan: rolls over to gnaw on the brush
Deku: Why can't you do this yourself, anyway?
Kacchan: No thumbs
Deku: that's the most useful thing you've said all week

Deku, bursting into Kacchan's room after hearing hissing and yowling: Kacchan what's wrong?!
Kacchan, scratching at the mirror: THERE'S ANOTHER CAT IN MY ROOM GET HIM OUT
Deku, sighing: Kacchan that's a mirror
Kacchan: I DON'T CARE WHAT THE DAMN CAT'S NAME IS JUST GET IT OUT

Uraraka: carrying a big box out to the recycling
Deku: oh! Can I have that?
Uraraka: Sure! What for?
Deku: Um, just stick it on the ground right there
In the distance: rapid footsteps growing louder
Kacchan: dives into box and skids across the floor happily
Deku: For that

Kacchan: Rolls around in a sunny patch on the floor
Also Kacchan: Yawns and stretches cutely
Also Also Kacchan: Mews and purrs happily in his warm patch
Aizawa: Please put your phones away and get back to work
The rest of 1-A: Sadly stop filming and return to their desks

Kacchan: Walks into Deku's room, looks at the bed, at all the blankets and pillows, at the cardboard boxes scattered around, at Deku's lap, at the rug on the floor
Also Kacchan: lies down on the hardwood floor for a nap

Kacchan, holding a string: Where's Deku?
Kirishima: He went out
Kacchan: I need him
Kirishima: Are you... Trying to play? I can wiggle the string for you.
Kacchan: No, only Deku

Kacchan: Desperately shoving his head in a paper bag
Kirishima: Uhh you okay there bud?
Deku: He's trying to get in the bag but he doesn't fit
Kacchan: I CAN FIT SHUT UP LOSER
Deku: He's been doing this for two hours

Kacchan, slamming Deku's door open at 3am: DEKU I DID IT
Deku, half asleep: Huh? Wh- What did you do, Kacchan?
Kacchan, with a paper bag on his head and a lot of bruises from stumbling up the stairs blindly: I GOT IN

[Side note: The inspiration for this arc]

Kacchan: Whines pitifully and paws at Deku on the couch
Deku: Aww Kacchan is it cuddle time?
Kacchan, as he climbs into Deku's lap: Shut up nerd I don't do cuddles
Deku, stroking Kacchan's hair and scratching his kitty-ears: Of course not, baby, I don't know what I was thinking

Deku, putting a pile of freshly-washed laundry down on his bed: Ahh, perfect, now to open my closet so I can hang my clothes
Also Deku: Turns around to pick up his first shirt
Kacchan: Curled up taking a nap in the warm clothing
Deku: WHERE DID YOU EVEN COME FROM

Later, after Kacchan leaves
Deku: There, laundry hung! Now let me make my bed with these clean sheets...
Kacchan: Appears on the mattress, batting at Deku's hands as he tries to make the bed
Deku: HOW

Krrk krrk krrk
Deku: What's that sound?
Scrrtch scrrt scrrttch
Deku: Kacchan is that you?
Ripp ripp ripp
Deku: Kacchan what are you- NO, BAD KITTY, DON'T CLAW THE ALL MIGHT PILLOWS
Kacchan, staring Deku dead in the eye as he continues clawing: Feed me

Kacchan: kneading Deku with his paws and purring
Deku: Kacchan you are very cute and I appreciate the attention but you're not exactly light and your kneading kind of hurts
Kacchan: Purrs and kneads harder

[Heading to bed again now but will continue tomorrow!]

Until then, if you feel like helping buy my babies snacks, here's my ko-fi link and also photos of said babies

(One of them is having some medical issues right now so she appreciates the treats)

http://ko-fi.com/saysionkofi 

Kacchan: Staring intently out the classroom window
Aizawa: Bakugou, is everything okay?
Kacchan: Chrrrrrrrr
Deku: I think he's watching the birds, Sensei
Kacchan, quietly: Let me at 'em

Kacchan: napping with his paws out in front of him
Deku: Gently holds his paw
Kacchan: Pulls his paws in without waking up
Deku:

Kacchan: Chrrrrr
Deku, holding him back: Tokoyami is a classmate you can't hunt him!!
Kacchan: B i r d

Deku, patting Kacchan on the edge of the bed: Sorry Kacchan I have to go, I'm meeting All Might
Kacchan: Whines
Deku: I'm sorry Kacchan I'll be back later, you can wait here if you want
Kacchan, flopping his entire bodyweight against Deku's stomach: But if you leave I'll fall

Deku: Kacchan I'm leaving, please sit up so you don't fall
Kacchan: You can't leave you'll make me fall
Deku: Kacchan please
Kacchan: You are stuck here, give me pats
Deku, sighing: You can have five more minutes, I'll text All Might
Kacchan: Heh, sucker

Kacchan, crawling into bed with Deku: It's cold
Deku: Aww baby c'mere
Kacchan, burrowing under the blankets: Must find warm
Kacchan, squeezing between Deku's legs: Ah yes, warm
Deku: Are you satisfied now?
Kacchan, going crazy in the blankets: Who turned out the lights?!

Aizawa, giving the entire class a stern look: I'm disappointed in you all, I expected you to take care of the communal property we provided for the dorms. Will anyone tell me what happened to the couches in here?
Kacchan, dragging himself along the couch by the claws: No clue

Uraraka, walking back into the dorms with her friends: Holy cow who trashed the common room?!
Asui: Oh my Gosh we've been robbed!!
Kacchan, pushing the last plant off the bookshelf and watching it shatter: Holy shit when?

Kacchan: Licking his paws, gets distracted by a bird
Kacchan's tongue: Stays hanging out as he watches the bird go by
Deku, giggling: Pokes Kacchan's little blep tongue
Kacchan: Glares, but doesn't put his tongue away

Deku: Lying on the couch watching a movie with his friends
Kacchan: Crawls in, grumbling, dragging a blankie with his teeth
Deku: Hi Kacchan, are you joining us?
Kacchan, throwing the blankie over Deku's lap and curling up on top
Deku: Ah okay, come get warm
Kacchan: Purrs

Uraraka: You understand him way too well
Deku, giggling: He can still TALK, silly
Uraraka: But... He didn't...
Deku: He didn't?