What happened that made George stop playing dirty tricks on Lenni?

Answer 1

George had told Lennie to jump into a river. Lennie did so but George did not realize that Lennie had not learned how to swim. Because of this, Lennie almost drowned and George jumped in to save him.

Answer 2

George realized that his actions were hurting Lennie's feelings and damaging their friendship. He decided to stop playing dirty tricks on Lennie because he cared about him and wanted to maintain a positive and trustworthy relationship.

Answer 3

George told Lennie to jump in a river, so he did, but Lennie couldnt swim at all he nearly drowned.