Location: Yulgar's Inn on the first floor, in the room past Uldor and Aquella. Drink the potion on the table.

Me: Wow! That potion I just drank shrank me down to the size of a mouse! That teaches me not to drink from strange bottles lying around in the Inn!
Me: That mouse hole looks interesting. I wonder what's in there? Probably just a mouse...

Snail

Spider

Smelly Rat

Snake

Me: Yes! I found my way back out of the hole. I wonder what will happen next?

Kitten

Yulgar

Me: What a curious adventure I've had! Whoah! I feel funny... I think the potion is wearing off...

Source

Suikoman444, http://forums2.battleon.com/f/tm.asp?m=3729783