Here's another idea that's been in my head for a while. A story about Superman (Superman the Animated Series) and Batman (Batman The animated series) teaming up with Disney's Hercules and Aladdin respectively.

Premise: Clark and Bruce at a charity Gala when a villain with mystical powers and a small group of their respective enemies crash the party. Suiting up, the heroes jump in and thus leading to said heroes and villains ending up in another world. Superman ends up in a land resembling ancient Greece. Luckily he meets an ally in the form of Hercules. Unfortunately, the villains and their leader are causing trouble for the locals.

So both heroes team up and learn they are not so different.

Meanwhile, Batman ends up in vast sandy Desert where he's found and picked up by a band of traveling merchants. Attack by bandits leads to Batman meeting the hero of Agrabah, Aladdin. Genie instantly recognizes the Dark Knight. But before they can help him find Superman and return them home, they arrive in Agrabah to find everyone has been turn to stone and something has been stolen. Luckily the Aladdin has the World's greatest detective to help.

Now Batman must deal with magic, monsters and one very enthusiastic fanboy with Semi-Phenomenal, Nearly Cosmic Power.

REALLY good idea. Heck, Aladdin and Hercules even met during a crossover adventure in Herc's animated midquel series. So, yeah, the big climax has all four of the main heroes uniting at the end.

And, yes, I could see the culture shock. And very good lead-off to the crossover at that.

The villains (minus the main one):

On Batman's end: the Penguin's goons, Killer Croc and the Scarecrow (Croc and Scarecrow doing kind of a "Brains and Brawn" type deal - Croc being the brawn and Scarecrow being the brains).

On Superman's end: Members of Intergang, Metallo and the Toyman.

On Hercules's end: Hades (naturally) and a fair number of his monsters.

On Aladdin's end: Well, obviously one of the more dangerous bandit gangs in the series, Mirage and her monsters. 

All that would be missing would be a good hypothetical replacement voice actor for Kevin Conroy.

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Thanks. And those would be cool ideas.