The Cheerleader Effect

Barney explains the Cheerleader Effect using a collection of women at the bar. One of which looks strikingly a lot like Marshall. Oh and Barney finds out he might be a father.
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How I Met Your Mother Season 4 Episode 7 Quotes

Robin: Anytime you even hear the word kids you get two little lactation stains on your shirt.
Ted: Thank God you're not a mom. You are such an ice queen, any baby nursing from you would get brain freeze!

Lily, no part of Barney Stinson does less than 110%. If one of my Michael Phelps' got loose, he's goin' for the gold!

Barney [referring to possibly impregnating a woman]