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).
Barney might be crazy, but he’s usually onto something about the weird psychology of attraction. [S6E11] The Mermaid Theory
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. In this episode, Barney’s "Mermaid Theory" posits that
The hilarious visual of Marshall seeing Robin as a literal manatee, then watching her transform into a mermaid as the "clock" runs out. Marshall is terrified of the "Mermaid" transition, while
Drive a group of angry brutes to glorious victory and elevate your father's ludus from the muck and mire of shameful defeat, restoring it to honour via ruthless bloody victory over your opponents.
May Jupiter himself hear of your exploits.