Snickers is a brand name chocolate bar made by Mars, Incorporated. It consists of nougat topped with caramel and peanuts, enrobed in milk chocolate.
To keep Peter from feeling left out when Stewie celebrates a birthday in "Chap Stewie", Lois bakes him his own cake. Peter blows out the candles on both and declares that he gets double wishes. Meg is struck by a meteor as the first wish which breaks open to reveal a Snickers bar as the second wish.
In "You Can't Handle the Booth!", Peter can't hear over the sound of Meg's Snickers wrapper.