Substitute DE: Crossover canon

[spooky-lemur.livejournal.com]

 So I'm currently listening to the audiobook for Museum of Thieves which is narrated by Claudia Black of Farscape and SG1 fame. I've also got an audiobook of The Odyssey read by Sir Ian McKellan (and let me say Magneto reads a very good Homer). I've also seen a certain partying ninja turtle on both Heroes and House. And I've seen Elle Bishop (from Heroes) and Goldilocks selling Makeup (which is really weird when you think about it) but I am sure I am missing much more.

So my question today is, what canons have you seen mixing? And not necessarily official canon; just actors in other works, narrating books, or what have you. Bonus points for the most crackiest.