The instances of phrases like "Eat me!" and "Bite me!"
An ad campaign where Red and Yellow quit their jobs through a strongly worded letter to Brown. Among the things they want to do with their free time are "breaking down in public and going into rehab". The letter ends with "Go fondue yourself".
There's also the one with Glee cast member Naya Rivera. Red sings "I Would Do Anything for Love (But I Won't Do That)" as he is subjected to things such as being baked into a cookie, and slathered with frosting. Then at the end, he is being bitten by Naya and two other hot girls, and he shouts, "It hurts but I kinda like it!"
On one occasion, Green flips out at Dennis Miller for seemingly trying to imply that the rumors about her (i.e. that green M&M's are aphrodisiacs) were true.
A scenario promoting M&M's Ice Cream Treats shows Red and Yellow trapped in a frozen wasteland that is revealed to be the inside of a grocery store freezer. Yellow then notices his 'M' is much smaller than usual.
Yellow: Hey, what happened to my 'M'?
Red: It's called "shrinkage".
The Masterfoods "Wheredafungo" promotion features advice to insert fun into one's work, such as funny words in a business call.
Yellow: Our numbers indicate that sales are way up in Lake Titicaca.
Ms. Brown's debut advert showed her annoyance with people assuming she's naked because her shell is brown. Cue Red walking in, declaring "So it's that kind of party!" and stripping off his shell while dancing to "Sexy and I Know It".