Stewie builds a body switching machine. Meanwhile, Peter and Lois try to bring thee sex back to their marriage.
Brian strikes out with a woman at a bar and feels bad about himself.
Lois tries to get Peter to have sex with her but he refuses, saying he's not interested. Lois complains that he hasn't had sex with her all month and that she fears the spark in their sex life is gone. She tells him that she called together a "sexual retreat" for the both of them, where they would go out of town to a resort, to learn about having fun sex again.
Stewie pities Brian and builds a Body Switching Device to swap their bodies so he can straighten out Brian's life. Brian accepts to the body switch but Stewie first alerts Brian that although they'll switch bodies, they'll still have their own vocal chords for some reason, so they'll need to try to imitate each other's voices. When they switch bodies, Brian has a bit of trouble wielding Stewie's giant head. However, Stewie has far more trouble than he could have imagined, when he tries to live Brian's life. He attempts to get him a job as a college professor but ends up being mocked and ridiculed by his students. Stewie later tries to get Brian a date at the Drunken Clam, but his sexual ignorance gets him hooked up with a prostitute named Sugar. Stewie runs away and Sugar yells at him for "stiffing her", despite the fact that she had not yet performed any sexual acts on him yet. She gets her pimp, Anton to chase Stewie with a crowbar, but Stewie uses his four fast dog legs to outrun him.
When Stewie returns home, he admits that Brian's life is harder than he thought and they attempt to return to their own bodies. Unfortunately, during the body swap, Peter and Chris burst into the room, fighting and interfere with the process. This leads to Stewie switching bodies with Peter as well as Brian switching bodies with Chris. Chris and Peter's fight also destroys the body switching machine, so they can't undo the body switch. Although it's safe for Chris to know about what happened, Stewie still needs to keep it a secret from Peter. Utilizing his new body, Stewie pretends to be Peter's reflection in the mirror, which soothes all of Peter's suspicions.
Stewie paces the living room, pondering how they can fix the time machine, but as Chris points out, the real problem is keeping this a secret from the public. Just then, Quagmire, Cleveland, and Joe come to the door to see Peter. This puts Stewie on the spot and he tries to fake a Peter impression. Quagmire immediately knows exactly what happened, so Stewie punches him in the face, knocking him out cold. He picks up Joe's wheelchair and dumps him out and uses the chair to slam Cleveland on the head. As Joe reaches for the telephone, Stewie stomps on his head, thereby incapacitating all three of them. Stewie says how much he enjoys now having a bigger and stronger body, as it makes attacking people so much easier, as he throws the bodies of Peter's friends into the basement. However, he does admit to that being way too close of a call and says that they're still not out of the woods, what with them still being stuck in each other's bodies. Before Stewie can think of a way to fix the body switching device, he finds his position to get even more precarious because just at that time, Lois tells "Peter" that it's time for them to go on their sexual retreat.
Brian and Chris, with Peter in tow, try to follow along to switch everyone's bodies back, but a run-in with a prostitute and her pimp that Stewie encountered earlier in Brian's body results in a car chase that ends when they smash into a power pole and a fallen transformer amplifies the device so that most of the town swaps bodies. Trying to fend off a horny Lois, Stewie coaches Brian through rewiring the device and placing it on a cell phone tower where he can get it struck by lightning, reversing the effect for the most part, although Herbert manages to land in Peter's body to have sex with an unsatisfied Lois. Lois admits that the time has come for her sex life and that she's just too old to enjoy it like she used to. Herbert, equally as displeased tells Lois that her "being too old" is in fact, part of the issue.
- Meg Griffin
- Glenn Quagmire
- Cleveland Brown
- Joe Swanson
- Ida Davis
- Jerome Blackmar
- Tom Tucker
- Herbert the Pervert
- Joyce Kinney
- James William Bottomtooth III
- Tricia Takanawa
- Kevin Swanson
- Susie Swanson
- Carter Pewterschmidt
- Babs Pewterschmidt
- Floyd Wetherton
- Connie D'amico
- Principal Shepherd
- Greased Up Deaf Guy
- Kool-Aid Guy
- Mayor Adam West
- Ollie Williams
- Live Studio Ostrich
- God (Cameo)
- Shiva (Cameo)
- Muriel Goldman (Tombstone)
- Diane Simmons (Tombstone)
- Donna Tubbs-Brown (Mentioned)
- The title is an inversion of the phrase "Flip the Switch".
- The show calls on the audience to pay attention when Stewie explains that even though they have swapped bodies, their own voices will be heard, in reference to the trope, "Voices are Mental".
- Brian has trouble wielding Stewie's giant head.
- Brian notes that all of Stewie's inventions stop working, when they most need them.
- List of switched bodies:
- Brian and Stewie
- Peter and Stewie
- Chris and Brian
- Joe Swanson and Consuela De La Morrela
- Tom Tucker and Herbert the Pervert
- Joyce Kinney and James William Bottomtooth III
- Tricia Takanawa and Ollie Williams
- Glenn Quagmire and Cleveland Brown
- Donna Tubbs-Brown and Bonnie Swanson
- Kevin Swanson and Susie Swanson
- Carter Pewterschmidt and Death
- Babs Pewterschmidt and Floyd Wetherton
- Meg Griffin and Connie D'amico
- Principal Shepherd and Greased Up Deaf Guy
- Ida and Jerome
- Brandy and Pedro
- Bruce and Kool-Aid Guy
- Live Studio Ostrich and Fouad
- Muriel Goldman and Diane Simmons
- Peter Griffin and Herbert the Pervert
- Diane and Muriel's tombstones, reveal they were born in 1970 and 1968, respectively.
- Lois is unaffected due to already being in Weekapaugh at the time of Brian's car wreck, although the distance does not seem to affect Brian's placement in Peter's body, due to Stewie, in Peter's body, using the phone, and the body-switching electrons going through the phone lines.
- Peter's popcorn trick on his crotch is in reference to a scene in the film Diner.
- Lois' smashing of the hotel bathroom door parodies that of Jack Nicholson in The Shining.
- After bursting in, Lois declares "Munch a bunch of Fritos," parodying a Fritos corn chips ad campaign of the 70's.
- Stewie/Brian's attempt to teach poetry and the instruction to tear out pages is a reference to Dead Poets Society.
- Ollie in Tricia's body references Freaky Friday, referring to multiple Disney body-swap comedy films that share the name.
- Jerome asks if he is "doing a Madea", a reference to Tyler Perry's character.