[s6e11] The Mermaid Theory Here

In this episode, Barney’s "Mermaid Theory" posits that any woman—no matter how unattractive she initially seems—will eventually become beautiful to a man after enough time spent isolated together (the "clock" starts ticking immediately).

The gang tests this theory when Marshall and Robin start hanging out one-on-one. Marshall is terrified of the "Mermaid" transition, while Robin is offended she isn't already a mermaid. Meanwhile, Ted and Zoey’s friendship hits a snag as they navigate the blurry lines of being "just friends" when there’s an obvious spark. [S6E11] The Mermaid Theory

The hilarious visual of Marshall seeing Robin as a literal manatee, then watching her transform into a mermaid as the "clock" runs out. In this episode, Barney’s "Mermaid Theory" posits that