I've started a number of threads on topics like this in the past, so I figured, why not just make one big thread devoted to any such situation people can think of?
Let's start with a short that was just released on Disney+ today, Once Upon a Studio! Here's the big group shot, apparently with 543 characters...
Instead of trying to name each one off the bat, I'm having trouble locating a few that I know are in the short. Although they're in the short, they might not have made it into the group shot.
Mrs. Krunklehorn / Robinson
Robin (Back to Never Land)
Cinderella's two bluebirds
Gazelle
The Magic Carpet
Fifi (Beauty and the Beast)
People say the Wolf from Peter and the Wolf and Squeaks from Fox and the Hound are in there, but I think it's pretty clear they're not.
And, of course, anyone is welcome to post their own such photos!