Asklemmy

Malazan / Discworld.

Just about any pair of characters would be amazing.

Its always sunny in Reno, where the gang are regular delinquents that Renos finest have to deal with

The 90s shows ReBoot and a modern day MMO. Any, really. It would be badass to see the Guardians get stuck in an MMO and try to beat the MSQ to escape, all while fighting a virus that infected the game. It would be like Sword Art.

I really wanted the Men in Black/21 Jump Street crossover that was teased a few times before being cancelled. Instead of finding a way to make it happen, Sony dropped the stinky turd MIB International which probably killed the franchise 😔

I'm pretty firmly against crossovers unless they are particularly compatible with each other. Unless it gels just right it feels pandering and lame. Smash Bros for example worked hard to make the disparate cast fit in with each other with subtle design changes. Ready Player One on the other hand...

X-Men and other super hero-esque media works. DC and Mortal Kombat works when you throw in magic to offset the power inbalance. (Although, I never questioned Marvel Vs Capcom's power scaling. Hsien-Ko and Phoenix Wright casually kicking Thanos' wrinkled purple ass never made me think twice.)

I'ld like Capcom to collapse more of their fighting and beat-em-up properties into Street Fighter. Hsien-Ko makes about as much sense in Street Fighter as half of the villains.

Star Trek/Re-Animator. The ultimate Jeffrey Combs picture. A cryogenically frozen Herbert West is revived on DS9 and gets to doing what he does best - undead monstrosities. Parts of the station are sealed off and eventually the only ones who can stop him are Weyoun and Brunt.