[s6e11] The Mermaid Theory Here

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.

The hilarious visual of Marshall seeing Robin as a literal manatee, then watching her transform into a mermaid as the "clock" runs out. [S6E11] The Mermaid Theory

Barney might be crazy, but he’s usually onto something about the weird psychology of attraction. The gang tests this theory when Marshall and

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 hilarious visual of Marshall seeing Robin as