Ted is busy teaching Barney in his class, "Robin 101," when Robin herself enters the classroom and the two boys are very shocked.
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The Barman and Robin are struggling a bit when Barney is not being a sensitive enough of a boyfriend, so he eventually enlists in Ted's class for help.
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Ted offers Barney help with his relationship with Robin in the form of a class cleverly entitled "Robin 101."
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How I Met Your Mother Season 5 Episode 3 Quotes

Don't cry in front of her, and whatever you do, don't cry in front of her four times

Ted [about Robin]

Funny thing, and this is just me, I like my balls attached to my body instead of rolling around next to some eyeliner in Robin's purse. Stinson out.

Barney