For the Big O decoy seen in Season 2's "The Creature Whisperer", see The Big O (Decoy).
For the current Big O who was formerly known as Ms. O, see Oprah.
The Big O was the head of all Odd Squads. He can only count to five, and carries two toys with him. He also has an impersonator.
In the movie, he was forced to shut down all Odd Squads when Weird Team rose to power, but reopened them after the Daves invasion.
As of the Season 2 finale he has stepped down from his role as Big O and is now retired due to expressing a desire to attend kindergarten, and has promoted Oprah in his place instead.