>>151059329 (OP)
We start with a flashback and find out that the "Tony Robbins" in one of the earlier Family Guy episodes who swallowed Peter whole, was actually Stan. Stan explains to the family that because of the experimental defenses he set up in the house decades ago, the toxins they emit will make them crave, and give them the ability to swallow a human whole. When it happened to Stan he impersonated Tony Robbins and swallowed Peter Griffin. It's never explained how Peter is still alive after that.
The rest of the movie goes as follows:
Stan swallows Peter (again)
Francine and Haley swallows Lois, Meg, Chris, Stewie, and Brian
Steve, Roger, and Klaus, and Jeff are upset because they don't get the Griffins and have to settle for whoever's nearby.
Roger swallows Quagmire, who has mixed feelings
Eventually they swallow everyone in Quahog and the craving stops.
The Smiths are now round like balls and Steve wonders how they're gonna get back home because they can't fit in the car. Stan says not to worry because while the toxins' effect is still in place, they can roll themselves around without much harm. The Smiths roll themselves in the homeward direction while singing Proud Mary ("Rollin, rollin, rollin on the river")
