Birthday Boy

Birthday Boy is a human and one of the main characters on Cubey World. He is a go lucky birthday kid with blue shirt, birthday hat and napkins, Birthday Boy has an insatiable appetite. As his name implies, his primary craving is cookies, but he can (and often does) consume anything and everything, from apples and pie to letters, flatware, and hubcaps. When Cookie Monster eats something, he makes a very distinct, loud munching "noise", often interpreted as "OMM-nom-nom-nom..."

Origin
Jim Henson's Designs and Doodles explains Cookie Monster's early life:"“In 1966, Henson drew three monsters who appeared in a General Foods commercial that featured three crunchy snack foods: Wheels, Crowns and Flutes. Each snack was represented by a different monster. The Wheel-Stealer was a short, fuzzy monster with wonky eyes and sharply pointed teeth. The Flute-Snatcher was a speed demon with a long, sharp nose and windblown hair. The Crown-Grabber was a hulk of a monster with a Boris Karloff accent and teeth that resembled giant knitting needles."

Cubey World
The monster gained his signature blue fur when he first appeared in the premiere season of Cubey World, as one of several recycled stock monsters that would appear in Muppet inserts. Early on, he often appeared as a foil to Ernie and Kermit, destroyed property used during lectures, and sometimes acted fussy if he didn't get his way. The monster's ravenous appetite for inedible objects was also established, devouring everything from letters to ukuleles.

Eating Cakes
Birthday Boy has devoured hundreds of cookies in his 40-plus years on Sesame Street. However, the cookies used on the show are not really cookies at all. Prop makers instead used rice crackers, which are painted to resemble cookies instead, as the oils from the actual food would be damaging to the puppet.[1]

On The Furchester Hotel, Cookie Monster's cookies are made from actual cookies, using only certain types of ingredients when baking. They are then painted and colored hot glue globs are used as chocolate chips. For use in the series, they typically bake 200 cookies per week.[9] Approximately, a total of 1500 cookies were baked over the course of the series.[10]

At a 2014 Nerd HQ panel at San Diego Comic-Con, David Rudman claimed writer Tony Geiss once mistakenly ate a couple prop cookies, unaware they were fake.