Sunwoo and Eric said they have so much similar looking underwear that sometimes they grab other member's underwear and then they see each other wearing it and are like "???????"

For more context: Sunwoo once came out from the shower and Eric saw him wearing his (Eric's) underwear. Sunwoo said it was a mistake because he thought everything on the sofa belonged to him.

About the clothes on the sofa, so The Boyz has a pile of clothes there. It's a mix of the member's clothes, underwear, socks. Eric and Sunwoo said when they need things they just go to the pile so they sometimes end up wearing things that don't belong to them.

One of them even said to the other members to collect their clothes until midnight, if not, they will discard the clothes. Sunwoo was beside it watching TV and said nothing belongs to him. But Eric said just one look and you can see 2-3 clothes in the pile that belongs to Sunwoo

(This honestly sounds so much like the story they told during the live when Sunwoo spilled food on Chanhee's desk. Sunwoo's chicken stew leftover was hanging around the dorm living room and TBZ placed the leftover under Sunwoo's bed and days after, they saw it was still there)