642. For one session - prefferably near April Fool's Day - have magic get very silly. I present the following examples:
a) When the cleric prays for spells, say s/he hears the following: "Hi, you've reached [god]. I'm not here to answer your prayers right now, so please leave a message after the beep. Bye! *beep*"
b) Have the writing in the wizard's spellbook suddenly change into Spanish. If he casts read magic, it turns into pig Latin.
c) Animal companions and familiars all start acting very animal-like. Owls fly off to look for mice, cats go after milk, and toads go up to the Damsel In Distress for the current adventure and claim to be a prince.