Thinking about crossover cliches...

[weirdweb]

...and I've been trying to compile a list of Most Overdone Crossover Cliches ever. (And maybe accompanying thoughts on how to turn them around.) So here's what I've got off the top of my head so far:

Generic:

• Everyone finds out about everyone else's Really Cool Secret.
• You think a character from Show A would be perfect with (or it would be so wrong you want to try it) a character from Show B, and mash the universes together and screw with existing canons simply so they can hook up.
• You insert a Sue/Stu into one universe and use them as the catalyst to unite the two shows.

Show Specific:

• Buffy/HP - (insert Scooby here) is invited to teach at Hogwarts.
• Buffy/HP - (insert Scooby here, but usually Willow) is sent to study at Hogwarts.
• Buffy/any show: Character from Show B becomes a Potential/Slayer. (HAS been done properly, but post-"Chosen" it happens so often I want to beat my head against a wall.) Even worse if said character ALREADY has super powers of some sort, so being a Slayer on top of that is usually overkill.
• Highlander/Buffy: Buffy becomes Immortal. (See above. She's already a Slayer. It's overkill.)
• Highlander/any show: Main character from Show B, despite all evidence to the contrary, is an Immortal and just never told anyone. (This is worse than a character finding out that he/she is Immortal, frankly.)
• Lord of the Rings/any show: Character B is sent to Middle-earth and becomes part of the Fellowship. (This is part of the reason I'm liking Lisette's "Equinoxium," aside from the research and careful thought she's put into it, it's set a few years AFTER the War of the Ring.)

Anyone have more to add? In fanfic genres that I'm not as familiar with?