The balloon is to display whether your no-hit achievement eligibility is active, correct?
That's probably doable.
Viewing post in Replayed this game some more. Some more suggestions.
But the no-hit achievement is sooooo counter intuitive to the way the game is played on harder difficulties. You are always getting swallowed, escaping, I-framing, getting hit with projectiles, I-framing, bumping into ghosts, I-framing; It's just so much better to just play on easy, get the achievement, then never look back. I know you ain't adding in a dodge roll, or heaven forbid, a parry? Can't it just be an easter egg on for the halls, or toggleable?
Then why not an extra joy? Getting out of bad luck situations at the cost of health is their precise function.
You can't give him a smart bomb because the one thing keeping you from using them, score, doesn't exist outside of stunting your upgrade progression.
And a parry or dodge roll would be disastrous because it would remove 90% of the need to position and manipulate enemies, or manage health. Japes is already barely affected by an amulet supposed to nullify him; we don't need him to turn into yet another character who can just block everything either.