Peter's up for a promotion at work, but he must first be sent back to repeat the third grade in order to qualify. Meanwhile, Frank Sinatra, Jr. returns to Quahog to open a new nightspot with Brian, and they enlist Stewie to make it the hottest new spot in town.

When Brian gets injured during a take of Peter's version of Jackass, the Griffins realize that Brian may be getting too old, so Peter brings home a new dog, prompting Brian to leave. Everyone else, however, loves "New Brian"; all except for Stewie, who doesn't like his constant happy attitude.

Peter gets a lasting supply of gasoline for the year, so the family decides to use it to take a road trip to the Grand Canyon. They pack up and hit the road, but it takes them a while to realize that they had forgotten to bring Stewie with them; when they do, they must make an explosive trip back home.

Mort Goldman accidentally steps into Stewie's time machine, so Brian and Stewie go back in time to retrieve him. Things look bad when they discover that they've arrived in World War II-era Poland, so they must travel to Nazi Germany to save Mort and find a way to safely return to the present.

Peter re-discovers his passion for the song "Surfin' Bird", a song so annoying that he drives everyone insane with it, prompting Brian and Stewie to destroy Peter's new record of the song. At the record store for another copy, Peter discovers Jesus disguised as the store clerk, and the two start hanging out.