My head is spinning
Lay in SM , main mentor Idol Producer
Tao , ex SM, main mentor in Produce 101 China
Kris ex SM ,judge in The Rap of China
Luhan ex SM in Hot blood dance crew (Along with Jackson who's also in idol producer )
Mc jin in The Rap of China and Idol Producer

Zhou Jieqong one of the members of Produce 101's I.O.I also in idol producer
Cheng xiao as mentor in idol producer but teammates xuanyi and meiqi in produce 101
Zhengting Justin in produce 101 and now winners in idol producer

Fan Cheng Cheng ( idol producer, nine percent) filmed Keep Running with Luhan
Jeffrey in Idol Producer is Jackie Chan's nephew, he has met kris wu too !
Tao worked with Jackie Chan in 'railroad tigers'
Lay also worked with Jackie Chan in 'kung fu yoga '

Not to mention connections with Wanna one
Li Xikan , Yu mingjun( idol producer) trained in Cube ent and are good friends with Lai Guanlin (who also made a video for them which aired in idol producer ep1)
Ding Zeren, Zhou Yanchen , Han Mubo(idol producer) trained in SM ent.

Zeren trained with renjun chenle kun of NCT
He Dongdong & li changeng (idol producer)used to be in FNC ent. Dongdong was a potential member of sf9

Zhou Jieqong is truly winning
She appeared in Produce 101 s1 as a contestant + winner
Also made an appearance on produce 101 s2
Was a mentor on Idol Producer
And now she'll make an appearance on Produce 48

Tao is also in The Street Dance of China along with Han Geng (ex SM artist , former Super Junior member)
Han Geng is also in Yuehua Ent. company along with Justin , Zhengting, wenjun, fan Cheng Cheng, xinchun,zeren,quanzhe (idol producer, nine percent)
Also in Yuehua are -

Also in Yuehua-
Cheng xiao (wjsn, idol producer)
Xuanyi,meiqi (wjsn , produce 101china )
Ahn Hyungseop, Lee Euiwoong (produce 101 , kpop idols ) also Choi Seunghyuk (produce 101)

Victoria [member of SM girl group f(x) ] is also a part of Hot Blood Dance Crew along with Luhan and Jackson

Chenle (NCT) is apparently friends with Qian Zhenghao (Idol Producer)!

Kun (NCT) is friends with Zhu Xingjie (Idol Producer ,Rap of China) Xingjie taught him magic
Apparently they used to be roommates in university !

Also Kun knows Ding Zeren !

Wang Yibo ( member of Uniq , in Yuehua Ent.) is a dance mentor on Produce 101 China along with Tao

Zhou Rui (Idol Producer) is friends with Sunnee ( Produce 101 China )

Hu Zhibang ( Idol Producer contestant) is good friends with Lucia (Wu Yingxiang) ( Produce 101 China contestant )

Xu Yiyang (俆艺洋) a former SMROOKIE. ( Sm ent predebut team) left the company.
And has joined L.Tao company which is founded by former Exo member Huang Zitao (黄子韬) in China
Cr- @chenwroteme

Xiao Jun ,from SmRookies , debuting in NCT soon, participated in X-FIRE (chinese show) along with Han Mubo (a former SM trainee )

Han Mubo also participated in Idol Producer and is a part of group Awaken- F.

Winwin from NCT 127 and NCT U attended the same performing arts school in China along with Zheng Ruibin (Idol Producer)

1st pic cr: @dearyangmi

Luo Jie, Lu Chenyu ( From Idol Producer and MR-X) , Xu Yiyang (former SmRookie, L.Tao Ent.) are participating in a Chinese survival show 'The Next Top Bang'

Mentor line up includes Kris Wu (ex SM, former Exo ) and Victoria Song (from the group f(x) , SM ent)