One of the key elements in "How I Met Your Mother" is the integration of flashbacks throughout episodes. Monday night's episode, titled "Platonish," was a major flashback to six months before the wedding we've been gradually getting through this season. 

Before delving into the past, we see a brief moment of the wedding to transition into it. Robin, along with Barney, Ted, and Lily, is sitting in the lounge crying over the bad news: as we learned last week, her mom is terrified of flying, and could not even bring herself to get into the plane to go to her daughter's wedding. Therefore, she won't be in attendance and of course, this breaks Robin's heart. Barney accepts the challenge of cheering her up. He then states his excellent track record with completing all challenges he's accepted, and Lily is shocked by this. "Diapers and samosas!" she shouts in reference to one particular feat Barney never accomplished.

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And now we're back at good ol' MacLaren's Pub with the gang! Ted and Robin are in the middle of one of their inside jokes, one that annoys the rest of their friends to no end. They salute every time someone says "Major" or "Colonel" (or anything sounding remotely like a rank in the military). Then, the two friends salute and repeat what was said. "Major Craving-for-a-Mojito!"

Barney shows up shortly after and explains his theory of being platonic with other people. He observes that only one pairing in the group is completely friendly only and nothing more. Who is it exactly? It's Robin and Marshall. In a hypothetical scenario on the show, Lily has a bunch of dynamite tied to her and if the pair doesn't make out, she and all of the customers at the bar will die. Scoot forward about twenty minutes, and Marshall and Robin are not even close to touching lips. Everything goes boom!

Lily notices that Barney only accepts his own challenges, so she decides to make things interesting by challenging him to accomplish some stuff. She finds them all nearly impossible to conquer, yet as we see through the rest of the episode, Barney can win in any situation.

First challenge: pick up a girl while talking like a dolphin. 

During all this madness, Ted and Marshall are at a basketball game, and Marshall confesses to Ted that Robin is still in love with him. Ted is overwhelmed and left speechless, but that ends as soon as his best friend says it was a lie. He does, however, notice Ted's reaction and sees that no matter how much it's denied, Ted's still in love with her. 

Surprise, surprise, Barney accepted and defeated the challenge. He got a girl's number to Robin and Lily's complete disbelief. Robin checks if the phone number is even real, and gives the girl a piece of advice: stay single for a while. Her judgment is going bad if she's giving her number to a guy who talks like a dolphin. Robin and Lily think the fun's over and they can no longer try to outdo Barney, but he insists on being given something else to prove them wrong with.

Second challenge: pick up a girl wearing a garbage bag…and talk without using the letter "e".

Barney asks for a girl's name. It's Elaine. He recovers from the possibility of losing the bet with, "How about I just call you…tomorrow?" She gives him the number. Smooth.

Robin's pretty fed up with Barney winning at this point so she intervenes. She pretends to be Ryan Gosling's personal assistant and tells a redhead at the bar that Ryan's interested, but super shy and so in order to approach her, he must work up his confidence by not watching her interact with any other guys. 

Robin goes back to the apartment and tells Barney to get the redhead. When he approaches her, she yells at him not to come closer. It's Ryan Gosling, she's not gonna screw it up. Or so we think. Barney pulls the "extreme method actor" bit and the girl believes he's actually Mr. Gosling after undergoing immense plastic surgery. 

Marshall continues to insist on Ted going after Robin one last time. He feels like it's in Ted's best interest to do so. Ted is slowly convincing himself, but he knows in his heart that trying to win her back will only result in him being heartbroken. His phone rings, and it's an unknown number. Ted answers; it's Hammond Druthers! Played by Bryan Cranston of "Breaking Bad" fame, Druthers was a minor character a few seasons ago. He is a renowned architect who managed the firm Ted once worked at.

So Druthers is calling to convince Ted to join him in a project in Chicago. Ted declines the offer, but not before Druthers leaves the opportunity open, so if he changes his mind, Ted can always say yes.

Lily is irritated by Barney at this point, so she just asks him to buy some diapers, and Robin chimes in that she wants samosas. He feels like it sounds too much like an errand, but they add the extra hurdle of doing that while getting yet another girl's number. 

Barney's at the drugstore, and he finds his target. She has her back turned towards him, and when she turns around, it's a doozy. Why, she's the Mother! Barney pulls his usual plays to get her digits, but she sees through it. The Mother wishes that Barney feel better and that things will be okay. "You will get through this," she tells him. 

Initially, Barney shrugs it off as something irrelevant, but when he goes to hit on another girl, he's haunted by the idea of being "sad". She goes back to the Mother, and asks her to explain. A while later, they find themselves sitting on a bench outside and chatting. "I think you were in love and you messed it up," she muses. She encourages him to go after the girl of his dreams, giving him the option to either keep playing or win.

Barney wants to win. He wants Robin, and he thinks twenty minutes will make it all happen. But oh no, the Mother is once again calling him out on the errors he's committing. She blatantly says this is the final chance he's getting, that it's going to take up all his time for it to happen. As for her? She shrugs and claims that her current boyfriend probably isn't the one. She's waiting for the right guy.

The most frustrating moment was Barney considering someone to set the Mother up with, but he draws a blank! Really, Barney, no one absolutely perfect for her comes to mind?!

Ted goes back to the apartment and sees that Robin is eating olives, though on their first date she handed him a plate of them and admitted to hating them. "I changed my mind," she tells him. That's all the encouragement Ted needs to fully decline Druthers's offer and to set his sights on winning Robin back. He decides to take things slow, to plan this out right. "There's no rush," he tells Marshall.

Little does he know that Barney feels the same way, and more than ever, he's planning everything out perfectly to work out in his favor.

And we arrive back at the wedding weekend, where Barney is reflecting on the girl he met at the drugstore, thankful she set him straight. His only challenge after speaking to her was to get Robin to fall in love with him.

Like Robin responded, "Challenge completed."

For now, because Ted doesn't seem to be letting go of his emotions towards her any time soon.

Next week, Barney's parents arrive at the Inn and he seems to be pulling a "Parent Trap" to get them back together! Will his insane plan work to mend his broken family?

WATCH: Preview for "Mom and Dad", premiering Monday at 8PM on CBS.

Reach Staff Reporter Gennyvera Pacheco here.