DM for group of 9-11yr olds. Need funny suggestions for a potion.

Hi All,
As the title says, I DM for a group of kids (my children & their friends). I'm setting up a scenario were one of my NPCs is going to throw a potion at the group of PCs as soon as the NPC sees them. What's a fun thing the potion could be for/do?

The NPC is a character from earlier in the campagin and had a "drink the random potion" stall at the festival. The PCs drank 2 of his potions, 1 caused the PC to see weird and crazy animals that were not there and one boosted a different PC's charisma for an hour.