Lily tries to get Barney and Robin to officially define their relationship while Ted worries about his first lecture as a college professor.
This episode provides examples of:
- Audience Participation: Variation: As Ted struggles to remember how "Professor" is spelled, he apprehensively adds a second F before stealing a glance at the students in the classroom... whereupon one quietly shakes her head in the negative, prompting Ted to change the F to an E (which she confirms with a nod to be correct).
- Bait-and-Switch: Ted mentions that the mother was in that classroom on his first day, with the camera lingering on a girl raising her hand. Turns out, that wasn't the mother. It was a girl who was likely trying to tell Ted that he was in the wrong room.
- Batman Gambit: Lily locks Barney & Robin in a room to have them define their relationship (as seen below) so they just say their boyfriend and girlfriend so Lily will get off their case. But, as Lily notes at the end, that's what they are, whether they want to admit it or not, meaning her plan worked.
- Brick Joke: Ted and Barney have a flashback where they're dressed in tuxedos at the bar, and Marshall complains that they never invite him to "Tuxedo Night." The Stinger has Marshall show up to the bar in a tuxedo and brag about how he didn't let Ted or Barney know it was "Tuxedo Night."
- Catapult Nightmare: Ted has a nightmare about how his first day as a professor will go. He shoots awake to find Barney rummaging in his room for condoms.
- Cringe Comedy: Ted's entire first lecture, in which he awkwardly embarrasses himself in front of the students that aren't even in his class, while missing his actual class.
- Detachable Doorknob: Lily traps Barney and Robin in Robin's bedroom by disconnecting the doorknob, in an effort to force them to define their relationship.
- Epic Fail: Being in the wrong classroom aside, Ted's first day as a professor immediately hits a road bump when he decides to write his name on a chalkboard... only to realize he didn't know how many Fs were in "Professor".
- Friends with Benefits: Robin and Barney repeatedly keep having sex and insist they are not a couple but are rather trying to figure out what they are exactly. The rest of the gang disapprove of this telling them to have "the talk".
- Gentle Giant: Brad proves to be this. He's 6'5" and muscular, but to mention being pretty much unfazed by a sucker punch from Barney, but his response to apologize for hitting on Barney's "girlfriend" is non-violent, friendly, and understanding.
- Gilligan Cut: Marshall encourages Ted to use his whip without even aiming it. Smash cut to them walking back to Ted's apartment, a noticeable lash across Marshall's face.
- Hypocritical Humor: Marshall admonishes Ted for treating his whip like a toy, despite him being the one who encouraged Ted to use it so willy-nilly and continuing to use it casually throughout the episode.
- Jerkass: Lily forcing Barney and Robin to define the relationship and going so far to lock them in Robin's room until they defined their relationship the way she wanted them to.
- No-Sell: Barney punches Brad while the latter is on a date with Robyn, who Barney has feelings for. Brad's reaction is basically blinking in surprise, causing Barney to cower in fear, fortunately Nice Guy Brad understands and lets it drop.
- Not Me This Time: When Robin finds her bedroom door locked, she assumes Barney locked it as part of roleplay and says their Safe Word so he'll unlock it. Barney informs her that he really didn't lock it, to which Lily, who's on the other side, reveals she did so the two of them can finally define the relationship.
- Not Where They Thought: Ted spends seven minutes teaching what he believes is his architecture class, only to find out that he's in an economics classroom.
- Relationship Labeling Problems: Robin and Barney start their relationship by having repeated sex but refusing to call themselves a couple, despite the clear evidence that they have feelings for one another. Their friends, particularly Lily, insist they actually find a good way to describe their relationship. Lily even locks them in a room and forces them to have "the talk" about defining their relationship. At the end, Barney and Robin decide to lie and pretend they're boyfriend and girlfriend... the joke being that they don't have to try that hard to pretend they love each other.
- Ten Minutes in the Closet: Lily locks Robin and Barney in Robin's bedroom and refuses to let them out until they've defined their relationship (with emphasis being on them reaching the definition Lily wants).
