NPR's guide to the running gags from the show.
G.O.B.'s name — George Sr. Oscar Bluth — is mispronounced.
5 episodes feature this joke:
Siri calls G.O.B. "gahb."
Sources: Joke data compiled by Adam Cole / NPR. Episode metadata from The TVDB via a Creative Commons Attribution 3.0 United States (CC BY 3.0 US) license.