George Oscar Bluth, Sr., or "Pop-Pop" to his grandchildren, is the patriarch of the Bluth family and the husband of Lucille. George Sr. was the CEO of the Bluth Company until the SEC started investigating him and he got imprisoned. In prison, George Sr. still tried to control his company through GOB while his competent son, Michael, tried to run it legitimately.
At one point, George Sr. escapes to Mexico with the evidence of him dealing with Hussein and fakes his death. He then sneaks into the Bluth home and lives in the attic, until eventually he is found, and put under house arrest.
By the end of the series, it is revealed that Lucille was the true mastermind and he escapes to Cabo at the end.
George Sr.: They cannot arrest a husband and wife for the same crime.
Michael: Yeah? I don't think that that's true, dad.
George Sr.: Really? I've got the worst (bleep) attorneys!
Narrator: And Michael finds it difficult to get his father out of jail.
Michael: You love it here?
George Sr.: Oh, I'm having the time of my life. Hey, T-Bone.