From issue 2.

Seems to be Brain Cells casting illusions of Clark to make a final push against Jon's confidence as Superman. We see a hint of this set up with Brain Cells being able to mimic Clark's voice, and that *really* striking a nerve with Jon. This may be where Jon surpasses the shadow of his dad-- at least insofar as raw power via what he assumed made him weaker.

Really hope this isn't the last we see of Brain Cells. He's low key funny, and the fact that he's somewhat of a trickster character whispering venom and sowing seeds of doubt and manipulation rather than just being a big guy to punch is really cool. Even while he's turn himself into a battleship, he's still doing things like using the city as a shield, manipulating Kara, and using projections of Clark to stop Jon.