Tip: Make sure that ALL exit-enabled pipes, doors, etc. have a screen exit defined, or they'll take you to Level 0, the "endless" bonus game. Unless Start+Select is enabled, the only way out of it is to reset the game.
It would be really cool if this boss used the hairstyle that he has in the credits and not Larry's.
This is rather easy to solve; after all, it is just graphic editing. If the original Iggy's hair does fit in the space this sprite has available, you can always edit it for your needs. You do not even need to use Iggy as a base to this sprite; with enough editing, you could have easily another Koopaling such as Larry.
Lunar Magic 3.11
Pixi 1.2.14 (I'm moving on to 1.2.15 now since it officially dropped while I was moderating this)
SA-1 Pack 1.32 (also tested without)
Another custom boss and it seems to work well from my testing, so it's accepted. Good note with the max shell speed value (even numbers only), since otherwise it can get messed up. Note for anyone that wants to use this, please don't set HP to 0. I'd imagine nobody would want to, but the boss doesn't like to behave properly if it initially starts with this.