Pondering Plans for Polymorphed PCs

(If you know who Rosehip and Cornelius are, begone!)

I have recently polymorphed all of my level-12 players into random level-12 monsters (limited to animals/beasts). They are going to battle some giant plants in their new forms. Should be funny.

I am looking for other ideas about fun or amusing encounters or challenges to present to my players while they are polymorphed - maybe something they must do to reverse their condition. I don't want them to stay polymorphed more than a session, but I do want to take advantage of the silliness of the situation as a break from the heavy stuff that's been going on in our campaign.

There are six of them, currently in the forms of: cauthooj, goliath spider, spinosaurus, tidehawk, kokogiak, and sky fisher. Ideas I am currently working on include:
- Introduce an NPC (maybe one they already know), who is terrified of them in their new forms, or alternatively, bravely tries to slay them
- Since they are now quite large, maybe something that would have been simple for them (like crawling through some ducts/tunnels or manipulating the instruments in an alchemical lab) becomes a momentous challenge
- They must play some kind of game, for some reason? Monster volleyball???

Any ideas are appreciated!

Side note: I'm also trying to figure out how to handle spellcasting in the new form. I want to encourage creative use of these creatures' abilities without relying on the PCs' existing spells, and therefore I'm thinking of counting these polymorphed forms as "battle forms," which explicitly prohibits spellcasting. This would include the kineticist's impulses. Is this too restrictive?