Ted and Marshall plan one of their nostalgic road trips to a pizza place in Chicago, but Lily joins them, making Ted feel as if the "bro time" isn't there. Meanwhile, Robin is at risk for deportation, and Barney helps her cram for the U.S. citizenship test.
This episode provides examples of:
- Artistic License – Law: There is no way Robin would be eligible to apply for American citizenship. She would either need an immediate family member (parent, child, or spouse) to sponsor her, or have been on a green card for five years, which isn't possible seeing as she was on a work visa less than a year ago in "The Possimpibile".
- Body Horror: Ted, presumably due to being high on caffeine, imagines Marshall and Lily merging into one blob-like being due to their intimate relationship.
- Both Sides Have a Point: Ted is mad at Marshall for bringing Lily along on their road trip because the road trip was just their tradition and he wanted them to have some time to hang out by themselves just like the old days. Upon hearing this at the pizza place, Marshall argues that he's a married man now and can't just ditch Lily on a whim like the old days. Eventually, they both realize the other person made good points and reconcile.
- The Cameo: Kenny Rogers as the narrator of the Sparky audiobook.
- Double Aesop: Marshall realizes that he needs to make time for Ted without Lily if he truly values their friendship, and Ted realizes he needs to give Marshall space to be a married man, thanks to the book about Sparky.
- Eagleland: Barney's citizenship test for Robin consists of quizzing her on various facets of American pop culture.Barney: Question one: (holds up a picture of the then Queen) Who is this?
Robin: Queen Elizabeth the Second.
Barney: No, the answer is Elton John. Question two: What the hell is this?
Robin: Oh, curling. It's a sport played by—
Barney: Wrong. The answer we were looking for was, "I don't care, it's dumb. Let's go buy something that's bad for us then sue the people who made it!" That's American, Robin. - Eiffel Tower Effect: Parodied. When Robin goes on a bender, Barney tries to dramatically show her she ended up in Toronto by opening the hotel room's blinds to show her the Toronto skyline. Except when he opens them, the only thing they can see is a solid wall of another building about 10 feet away blocking the entire view.
- The Food Poisoning Incident: Ted tricks Marshall into ditching Lily at a bed-and-breakfast so they can go to their favorite (unsanitary) pizza place before it gets shut down, but Marshall feels guilty and they go back to find that the B&B has pampered Lily into such a deep state of relaxation she didn't even notice they were gone. In any case, within minutes Ted and Marshall get violently sick from the pizza.Marshall: Baby, cut it out of me. Cut it out!
- Friend Versus Lover: Ted feels that Marshall has been ignoring him since he got married.
- G-Rated Drug: Tantrum. Which is technically a soda, but with high levels of caffeine enough to render someone hyper. According to Future Ted, it was eventually banned in the United States. (cue exploding mouse)
- Gilligan Cut: Marshall could not bear the thought of leaving Lily alone after Ted kidnaps him to go to Chicago. At first.Marshall: What are you doing? We can't just leave Lily.
Ted: She's got a backrub and a crumpet, she'll be fine. Relax. Have some fun.Marshall: I just abandoned my wife. How am I supposed to have fun?(4 minutes later, cut to the two jamming to "I'm Gonna Be (500 Miles)" by The Proclaimers)Ted: Hey, you really think Lily is pissed?
Marshall: (laughing while drunk on Tantrum) If she's pissed, she's pissed. - Moose and Maple Syrup: The night before her citizenship test, Robin gets drunk at the Hoser Hut and ends up traveling to Toronto. When Barney tracks her down, they go to a Tim Horton's where Robin feels alienated by everyone's friendliness and hockey references, making her question if she's even a real Canadian anymore after living in America so long.
- Overly Long Gag: The Sparky book tells us how much Sparky loved chasing balls by providing an absurdly long list of balls and ball-like things he liked to chase, which prompts a frustrated Ted to shut it off and ask Lily if she has to pee (she does).
- Pun-Based Title: Robin is "dueling" with herself about which country she'd rather be a citizen of.
- Reality Is Unrealistic: Barney is astonished that the Canadian five-dollar bill is blue and has kids playing hockey on the back. Which it does.Barney: It's like you want us to make fun of you!
- Running Gag: Lily having to pee, the stereotypes of Canada and the US, and Tantrum making you insane.
- Series Continuity Error: Flashbacks show Ted and Marshall driving to Chicago sustained on only jerky and Tantrum. However, a point was made in "Arrivederci, Fiero" that Marshall has always had a very firm rule about not allowing food or drink in his car, not even groceries.
- Sickeningly Sweethearts: Marshall and Lily have reached a point in their marriage that they exclusively refer to themselves as "we" and not "I".
- Spoiler Title: The "duel/dual" homonym spoils Robin's decision to be a dual citizen.
- Stylistic Suck: The Sparky book is presented as banal and boring.
- Take a Third Option: Robin, thinking she's too American for Canada and too Canadian for America, decides that Both Sides Have a Point and opts for dual citizenship.Robin: Instead of being a woman with no country, I'm gonna be a woman with two.
- Third Wheel: Ted, Marshall, and Lily's sideplot involves Ted feeling like a third wheel to Lily and Marshall since their wedding. In the episode, Ted and Marshall take a road trip to Chicago like they used to in college, but Ted is irritated that Marshall invited Lily who spoils the experience with her constant pee breaks and cheesy audiobook.
