Me love cookies. Me love cookies just as much as Cookie Monster. But, oh-oh, listen to this, Cookie Monster's cookies no really cookies. Shocking, me know! They… they rice cakes painted to look like cookies. Can you believe it? Me hardly can!
According to David Borgenicht's "Sesame Street Unpaved" (via The Great American Chocolate Chip Cookie Book), the reason Cookie Monster can't have any cookies is two-fold. The chocolate and oil in normal cookies would turn the fabric of the Muppets greasy, and we assume that it's no picnic scrubbing melted chocolate and crumbs from the fur of a Muppet to begin with. The secondary reason for the lightweight "cookies" is that, thanks to Cookie Monster's design, the "rice cookies" pass through the space of Cookie Monster's mouth and land harmlessly on the head of his puppeteer, preventing some messy bloopers.
Ok, me been lied to but me understand the reasoning. Now gimme real cookie. Nom nom nom!