shiny-pokemon-giveaways:

Contrary to what Gamefreak thinks, UB doesn’t stand for Ultra Beasts; it stands to Ultra hacked Bulbasaur. I got this abomination from Wonder Trade during this week’s WTW and honestly, they’ve become my favorite Wonderfail of all time.

Apparently it’s a Naganadel that’s a level 100, genderless, normal-type Bulbasaur from the very depths of Hell. Their favorite hobbies are consuming Pokebeans with their eyeballs and crashing the game.