Honest answer? Dancing stick figure guy on the title screen. I did it very early in the project, in a fugue state at 3am. It lingered and lingered there, with ppl wondering "Is this real? Is this the actual title screen?" and luckily by the end I think everyone had drank enough psychedelic koolaid to agree - stick figure man stays. The artist made some better art for his hands/feet, and that was that. He's divisive, but everybody at least remembers him :)

Lesson learned that I didn't expect - hmm. Ah, one good one: I spent a LOT of time worrying about stuff being "OP" or degenerately good. Well, turns out, people like OP stuff, or degenerately good stuff, at least in single player score attack games. My biggest lesson learned on the project: people experience your game individually. If they find something broken, in their head, they are the one to have found something broken, and it feels good. You don't have to design for the entire community at once. Don't over-balance your game. Embrace the jank.