M&Ms are a type of color-coated chocolate candy made by Mars, Incorporated, each of which has the letter "m" printed in lower case in white on one side.
In "Brian: Portrait of a Dog", Liza Minnelli uses blue M&Ms as a pick-me-up.
In "Brian Writes a Bestseller", Brian complains about all the M&Ms in a bowl being gray in reference to dogs' color blindness.
In "You Can't Do That On Television, Peter", Stewie claims that he has a peanut M&M stuck in his nose that his finger cannot reach.
A cutaway in "Turban Cowboy" shows a gay couple laughing at and criticizing a bowl of M&Ms set out.
In "Saturated Fat Guy", Peter sells "cereal" that is just M&Ms in Dr. Pepper.
A red M&M shoots Peter in the arm after the latter devoured all of the others in an advent calendar in "Christmas Crime".
In "A 'Stache from the Past", Peter tells Wild West that the M&M's World store in New York City sells jackets so bad that even Sinbad wouldn't wear them.