Well, I wanted to try this for myself as I was just in that area but I happened to find out something more interesting!
I charmed a chicken with Minsc's charm ability and when I clicked on the chicken, I noticed that it has the spell button enabled. Being curious, I clicked on it and found out that it gives me the same exact spell icon with the number 1 on it. I found out that even though the spell icon there looked dimmed out, I could click on it!!
Clicking on the spell icon cast a spell called "mimic glue", a very powerful spell which made all my party members glued to the ground (the efftect on their feet looks just like the grease spell).
I don't know if you guys knew this but I wanted to post it just in case. I would have never thought that a chicken could be a wizard. An easter egg I guess.
EDIT: I just found out that the chickens also have a special ability. Clicking on the special ability button allows them to cast "mimic acid"! So, I guess chickens use the same files as mimics when charmed. Interesting...