Not as good as the April Fools taunts, but still pretty awesome. These are the ones I've had so far:
Trick: Bombed with rotten eggs! (damage dealt; I think it's a Poison move)
Treat: Om nom nom roots! (Ingrain)
Trick: You got hit in the head! (confused)
Treat: Uhm, these candy taste weird... (some stats change)
-Special Attack sharply rose!
Trick: Doused with water! (damage dealt; Water move)
Trick: Your car was stolen! (Embargo)
Trick: You're haunted and you're going to die! (Perish Song)
Treat: You got some yummy seeds! (Leech Seed)
Trick: You've been taunted by those meddling kids! (Taunt)
Trick: You got scared by a real-looking costume! (damage dealt; I think this is Ghost type)
Treat: You got candy! (Health replenished)
Trick: Your arms were maimed!
- The foe's Snorlax's Ice Punch was disabled! (I guess punching moves are disabled)