@marisamusic Here is what I found...
(comments by other people, not me)
"Apparently he bullied Lay pre-debut. Not sure if it's true but so far we have seen Lay interact with most of the SMRookie kids besides Johnny. At the same time however, EXO's maknaes and Suho are still close to Johnny so it makes me wonder just how much truth is in these rumours. The maknaes I can understand especially since they're the same age as Johnny, but I doubt Suho would be close to him if it were true."
"The rumours wss he liked to start petty fights with Lay and Lay never responded. Like he didn't physically bullied him or anything. I honestly think it was just him being an obnoxious kid. But cfans are not going to let this go though. Not only Lay fans but c kpop fans too."
"There is a possibility that Johnny was not alone and Lay is a foreigner so it's not really impossible just because Johnny is younger."