It's from "Stewie Griffin: The Untold Story",specifically "Stewie & Stu's Excellent Adventure"
Season Four|Episode Eleven Perfect Castaway
no episode with this content
The episode is "Stuck Together, Torn Apart" from Season 3, episode #19
Stuck Together, Torn Apart
"stuck together, torn apart"
In episode 101,102
no episode with this content
D-a-m-m-i-t Janet
Lethal Weapons
The Third
Season Three's Stuck Together Torn Apart
The episode is "Stuck Together, Torn Apart" from Season 3, episode #19
Stuck Together, Torn Apart
Try Stuck Together Torn Apart
Unless I'm not remembering the first two episodes correctly I think the first thing that could be considered a flashback was in the third episode when Peter is recounting what happened at Cheesy Charlies, also in the same episode we flashback to Lois being stuck in the kitchen during Meg's first birthday.
Stuck on an island was created in 2012.
"stuck together, torn apart"
Stuck Together, Torn Apart