Motherfuck has the highest base Defense stat of all Flying-type Pokémon.
Motherfuck's base stats are the exact same value as those of the official Pokémon it is a fusion of: its HP, Attack, Defense and Special Attack base stats are those of Graveler, its Special Defense base stat is that of Tentacool, and its Speed base stat is that of Golbat.
This Pokemon seems to exist partially as a way to punish those attempting to play with self-imposed Nuzlocke restrictions. A player meaning to level-up his weaker Pokemon may put the one he's training at the front of the party, only to encounter Motherfuck and have no way to retreat.
There was an incident in which a certain user attempted to censor this Pokémon's name throughout the wiki, leading to them getting banned from the wiki for an entire year.
It is a fusion of a number of Pokemon who are extremely annoying to encounter to in the regular games: Graveler, Golbat, and Tentacool. Specifically, it owes to the fact that the former two are encountered in most later caves, while the latter is encountered in most water areas (which are also the places where the player can encounter Pokemon no matter where they are), and in the fact that Golbat can inflict confusion or poison, Tentacool can inflict Wrap or poison, and Graveler can use Self-Destruct or Explosion on top of Sturdy making them impossible to one-hit-kill.