Negative Numbuh 3's sharp teeth

Negative Numbuh 3 got her sharp teeth

The evil version of Kuki Sanban was originally featured in the TV series as Negative Numbuh 3 (or "Ikuk" since the names were backwards in their negative counterpart world), and is also used in Rainbowdash92's fanon works.

Later, she turns out to be a monster in season 9.