Ain't My Baby

Informing another party that a certain object, personality trait, person, dinner bill, bar tab, human baby, etc that does not belong to you OR would like to attempt to distance yourself from.

Waitress: "Thanks for coming in, guys. Here's the bill."

You: 'Ain't my baby". (friend pays the bill)

Doctor: "Congratulations, it's a boy". You: "Ain't my baby."

Cop: "Who's bag of booger sugar?" Kev: "Shit that ain't My Baby.'