Future Ted explains how nervous he was his first day of teaching, when he was trying to figure out what kind of teacher he would be; formal disciplinarian or laid-back peer. Before the first class, Marshall gives Ted the gift of a worn leather fedora and whip, just like Indiana Jones (in the alley later, Marshall is caught by the whip in the face).

Later, that night, Ted has a dream about his first day. As he starts the class, a girl raises her hand. She asks him who he thinks he is. A second student asks why he is teaching the class when he himself is a failure at architecture. A third student asks why he doesn’t have a hat and a whip. Another student quickly asks why he isn’t wearing any pants. Ted wakes in a panic, only to find Barney rifling through his nightstand for condoms.

At the actual first day of class, Ted starts writing, “Professor Mosby” on the board, but forgets if the word “Professor” has one “F” or two. This starts him off on a spiral of anxiety, alternating between stern authority figure, and laid-back buddy. The same girl depicted in his dream raises her hand, but following Barney’s advice, Ted is not taking questions during the first class. She was attempting to tell him he was in the wrong classroom.

Students start answering Ted’s questions about architecture, trying to dissuade him, but he only takes it as a challenge, and reworks their answers into positives. The real teacher eventually shows up, and humiliated, Ted runs across campus to his actual classroom. After being so embarrassed, Ted doesn’t have the energy to think about what kind of teacher he’ll be, and simply starts teaching.

Meanwhile, Barney and Robin have spent the summer sleeping together, but without any discussion about their relationship (“the Talk”). After the events of The Leap, Lily is ecstatic to have another couple to double date with, but the two quickly tell her they are not dating. They then lie to the gang all summer while hooking up secretly. When the gang walks in on the two of them making out on Ted’s couch, Barney and Robin talk about how much they hate talking about relationships and feelings. Later that night, Brad asks Robin out on a date to a hockey game.

At the arena, Robin is enthusiastic about the game, but admits that she feels weird going out with Brad, because she has feelings for Barney. Brad tells Robin she needs to have “the Talk” with Barney, and suddenly, they are put on the Jumbotron for a public kiss. Back at the apartment, Ted tells Barney that Robin is already his girlfriend according to his “Gremlins” rule. During a tuxedo-themed night at the bar, Barney explains you cannot get a woman wet (let her shower in your house), expose her to sunlight (date her before sunset), or feed her after midnight (breakfast together), or she will turn into your girlfriend. Barney rushes to the arena and interrupts the New York Rangers “Kiss Cam” by ineffectually punching Brad in the face. After apologizing, he and Robin are still unable to admit that they are dating.

Back at the apartment, after another night of sex, Robin tries to leave the room, but the doorknob detaches. Lily is outside, having sabotaged the door, and is waiting for them to have “the Talk.” Robin and Barney pass a few notes under the door with vague explanations, none of which satisfy her (punctuated by Marshall cracking the whip). Eventually, Robin and Barney decide to lie and say that they are dating, but their lie clearly has elements of sincerity, and the two leave the apartment hand-in-hand to go to brunch.

Later that night, after being left out of Tuxedo Night, Marshall shows up dressed to the nines at MacClaren’s.

“Definitions” is the first episode of season 5 of How I Met Your Mother TV series and aired on September 21, 2009.

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