Fanon Alert!
This article is of something that's FANMADE, and users own it instead of NinjaKiwi.

Oddity Bloons, as their name states, are odd. They are identical to Yellow Bloons except for one thing: Whereas normal bloons fly strictly on the track, Oddity Bloons fly off it and zip around randomly! Oddity Bloons still take the same amount of time to reach the exit as normal bloons, though. Oddity Bloons appear in the fan-made game Paper Bloons TD.
Blue Bloon

Is odd.