Conversation so far:
who were some recurring characters on pinky and the brain?
Merlin, H.G.
Wells, and Ivan Pavlov.
anyone else?
Snowball the hamster.
who was on there most often?
CANNOTANSWER.

Question: were there other recurring characters?
Self-contained rewrite: Besides Snowball the hamster, were there other recurring characters on Pinky and the Brain?