In Kick the Bucket , Fan apologizes to Paintbrush, though ignoring Test Tube, holding a bucket. Paintbrush accepts Fan's apology, while getting closer to the key.
Episodes suggesting a conflict
In Everything's A-OJ, Paintbrush and Fan have several arguments about how much work needed to be put in to win the challenge.
In Mazed and Confused, Paintbrush yells at Fan, saying he/she hates him, because the latter annoyed him/her by playing the piano while he/she is talking to Marshmallow, and apparently also putting on a game show.