It is self explanatory slang, referencing the exchange of one word (squirrel) with another (girl) in the name of a popular scout club that, in real life, sell cookies. It is merely a play on words and how they can sound so funny together.
As we walked up to the storefront Wallace said said "Hey look! The Squrrel Scouts are here selling their cookies" to wit he exclaimed "Squirrel ScoutCookies"!
The American Fortune Cookie is a complex sex position where the female lies straight on her back like a plank. The male sits on her mouth and places his penis in her nostril. The female begins tickling the male's feet while he shits in her mouth and begins to thrust at her nostril.
"I tried the American Fortune Cookie yesterday, and I swear i've never felt so relieved after."
"Chinese Fortune Cookies are so boring when you've tried the American Fortune Cookie."