Despite having two of the greatest comedic riff actors of all time "Robots" never has them interact. Any other examples of this?

I absolutely love the film, and with consideration would put it in my top 50 mainly off the rewatchability alone.

The jokes 'n' bits hit, the story is timeless(maybe more relevant now) with great voice acting and music.

The only thing that has bothered me since a kid was that it had robin williams and mel brooks, both heavily advertised and they never interact.

Is there any other film with all-stars of a genre that never interact?