Watch How I Met Your Mother Season 4 Episode 21 online via TV Fanatic with over 5 options to watch the How I Met Your Mother S4E21 full episode. Affiliates with free and paid streaming include Amazon, iTunes, Vudu, YouTube Purchase, and Google Play.
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When Ted violates the three day rule by texting a girl he just met, Barney and Marshall pretend to be the girl to mess with him.