A lot of unknowns here, like how much paint needs to be removed and how patient are you. Keep in mind that - short of a whole new paint job - there's no going back if you ruin your original paint.

Flip the bike over and put a dab of nail polish remover on the underside of the bottom bracket shell. Watch for any softening or lifting of the factory paint (assuming that's what the bike finish is). If the paint reacts in any way, immediately wipe with a wet sponge.

If the paint is unharmed, try a dab of your remover on the least conspicuous lizard. If the unwanted paint softens, try lifting or scraping with your fingernail. If this method shows promise, make a scraper out of a plastic eating utensil and CAREFULLY proceed with scraping at an acute angle, as if you were removing paint from glass. If this method succeeds without harming the original paint, and you have a small area that's clean, wipe it immediately with a wet sponge to remove the acetone.

If the nail polish remover shows promise with the lizards but only slowly, try straight acetone. Repeat the testing on the BB shell in case the stuff is too strong for the original paint.

No success with any of this? Talk to a custom car painter and pick their brains. However, don't rush into anything just because they recommend it - always test a method cautiously first. As Andy says, primum non nocere.