Brian and Stewie make a cameo appearance in a commercial for The Peanuts Movie merchandise from Target. Stewie is dressed in Charlie Brown's shirt, and Brian is dressed in Snoopy's Flying Ace helmet and scarf.
A 2007 Subway commercial had Peter reciting a poem called Ode to the Subway Feast. "Beat that, Jared."
A 2008 Coca-Cola commercial had Macy's Thanksgiving Parade balloons of Stewie and Underdog fighting over a balloon of a Coke bottle. It ends up getting caught by a Charlie Brown balloon.
A 2012 commercial had Stewie and Brian promoting Wheat Thins, which Stewie pronounces "Hweat Thins."
In Spider-Ham: Aporkalypse Now, Mojo decides Spider-Ham's World of Funny Animals needs to be more "mature", and reinvents Peter Porker as "Hammy Guy", with Mary-Jane Waterbuffalo as Lois, Captain Americat as Stewie, and Thrr, Dog of Thunder, as Brian.
In his review of The Thief and the Cobbler, during the scene where the Thief comes across YumYum bathing herself with a jewel-encrusted golden scratcher, the Critic plays the clip from "No Chris Left Behind" where Peter sells butt scratchers at a baseball game.
In his editorial "When Does a Joke Go Too Far?", the Critic addresses the controversy involving the Sarah Palin joke from "Extra Large Medium" and her response to it.
In the segment Send in the Clones from "Treehouse of Horror XIII", Peter makes a cameo among the many clones of Homer, a reference to criticisms that Family Guy is a clone of The Simpsons.
In "Treehouse of Horror XVI", executive producer Al Jean is credited as "Al 'Family Guy' Jean".
In "The Italian Bob", Italian cops look through a book of wanted felons containing a photo of Peter labeled "Plagarisimo", followed by one of Stan Smith labelled "Plagarisimo di Plagarisimo".
In "'Tis the 30th Season", it's shown that Disney World is constructing a new "Family Guy World" (also referencing Disney's acquisition of 21st Century Fox).
Stewie Mascot: I was the it-boy in 2006!
South Park: The two-part episode "Cartoon Wars" revolves around the news that Family Guy will do a joke about the Prophet Muhammad, and Cartman (who is sick of being compared to it) taking advantage of the ensuing panic to get the show cancelled.
Cartman: I am nothing like Family Guy! When I make jokes, they are inherent to a story! Deep, situational and emotional jokes based on what is relevant and has a point, not just one random, interchangeable joke after another!