I'm surprised Warner Bros let Disney put their characters in this movie

Actually, this movie was made by Touchstone Pictures. That's owned by the Disney Company...

I guess so. Too bad we never got a movie where DC and Marvel comics crossed over.

RIP
Eric Carr
1950-1991

The mandate was that their characters had an equal amount of screen time as Disney characters, which explains why Mickey Mouse and Bugs Bunny, and Donald Duck and Daffy Duck are on screen at the same time.

They originally refused when Disney asked, but Speilberg later managed to make them say yes. But even then the filmmakers were only allowed to use the Looney Tunes in a very limited and restricted capacity.

It's Disney owned property. If you go to Disney there's a whole section for Roger Rabbit and has been for over 20 years.

And nothing like it will ever happen again.