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 they hate him, because the latter annoyed them by playing the piano while they are talking to Marshmallow, and apparently also putting on a game show.