A Penis Butter and Jelly sandwich is when a guy cums in a girls vagina when shes on her period and there is a mixure of blood and jizz oozing from her slot. Her vag flaps supposedly being bread
I totally gave her a Penis Butter and Jelly

He lightly enjoyed the sight of her penis butter and jelly sandwich, he hated the taste
by NinjaSammichBear January 18, 2011
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A sandwich comprised of Penis Butter (Sperm, Semen, Ejaculate, Cum, Baby Gravy, Baby Batter, Horny Muffins, Knob Slime, Peace Grease, Dick Goo, Ectoplasm of The Nether, Spoofs...etc.) and the popular personal lubricant K.Y. Jelly. Often said as a joke or sang in substitution of the old "Peanut Butter and Jelly " song features on the 90's popular kids TV show Barney the Dinosaur.

Example of a joke with a friend if they don't like something.: (See Example Below)

Other example: look up Barney Peanut butter and Jelly and change the words, you will see where the idea came from.
"Wow, why don't you just go and eat a Penis Butter and K.Y. Jelly Sandwich!?"
by IronFistAlchemist June 18, 2018
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