What happened with Brock that makes him react so strangely to the mention of Professor Ivy?
Back when Brock came back, we were all delighted to finally get rid of Tracey, but we never really found out what happened to Brock and Ivy. Whenever someone would ask Brock what happened, he would fall to the ground and act really strange. From that I have drawn the conclusion that Ivy somehow took advantage of him in someway. Interpret that how you like, but that is what I think happened. For a more extensive explanation of what happened, click here.