It's a darn shame that there aren't more crossover episodes on TV. I grew up during the golden age of kids' TV crossover episodes. Who could forget the time when Hannah Montana, The Suite Life of Zack and Cody, and That's So Raven all came together in an epic three-part masterpiece? I was also privy to The Jimmy Timmy Power Hour, but only the part where Jimmy Neutron was in the Fairly Oddparents animation style because the Jimmy Neutron animation scared me beyond belief.
I hate to burst anyone's hopeful bubble, but unless characters are under the same faceless corporate media conglomerate, it's very unlikely that we'll find them meeting in any TV show or movie. Harry Potter and Luke Skywalker will literally never be friends, and we have to be okay with that. Fictional characters can only really meet in our memories, and of course, in the imaginations of Twitter users.