After Stewie gets his baby butt kicked by Joe’s infant daughter, he starts hitting the gym with Peter.
It seems like all of Stewie’s hard work is paying off until Peter drops a bombshell when he reveals just how Stewie got those six-pack abs.

Meanwhile, Chris starts to date a popular girl at school and quickly realizes that popularity is like physics – as in what goes up must come down.

Source: Stewie's Playground