Gary Oak, sometimes called Blue Oak or Gary Motherfucking Oak, is a running joke used online to undercut anyone bragging about an accomplishment by claiming the smug Pokémon rival already did it better3. The bit leans on the character's canonical habit of showing up at the worst possible moment with more badges, more Pokémon, and a smirk1.

A big part of the joke is fake awe at Gary's dominance, often described as his 'girth,' a bit lifted from a demotivational poster showing a roleplay chat where someone tries and fails to put Gary on ignore1. The humor works a lot like Chuck Norris facts, only Ash Ketchum is the eternal loser and Gary is the impossible benchmark3.

The typical format is a boast-and-deflate structure. Someone brags about a small win, and the reply invokes Gary, often with the exact tag 'Gary Motherfucking Oak,' to point out he already did it bigger3. A common convention is to escalate with badge counts, like 'you have 6, Gary has 8,' or to reference his 'girth' when someone tries to ignore or dismiss the point1.