“Slap Bet,” Season 2, Episode 9
“Sandcastles in the Sky,” Season 3, Episode 16
“Glitter,” Season 6, Episode 9
Highly inappropriate innuendos made learning fun in Robin’s second act as a Canadian superstar: the co-star (along with her BFF to the North, Jessica Glitter) of Space Teens, an intergalactic show about math and beavers.
“P.S. I Love You,” Season 8, Episode 15
We finally learn what happened to Robin Sparkles, and her transformation from peppy pop star into a grunge goth Robin Daggers, whose unrequited love for Paul Shaffer no one understood on Robin Sparkles: Underneath the Tunes.
2. The Slap Bet
“Slap Bet,” Season 2, Episode 9
After several mixups and unearned slaps taken, Barney decided he’d rather have Marshall slap him five times whenever he wanted instead of ten straight slaps in a row. Bad call, bro.
“Stuff,” Season 2, Episode 16
Barney staged his own awful one-man show in response to Lily making the gang come to her equally terrible show. Marshall slapped him for the second time after he insisted the group sit through his second act.
“Slapsgiving,” Season 3, Episode 9
Anxiety over Marshall’s slap countdown led Lily to declare no slaps on Thanksgiving. After Barney continued to taunt Marshall, Lily gave Marshall the go-ahead for the third slap, and the debut of “You Just Got Slapped.”
“Slapsgiving 2: Revenge of the Slap,” Season 5, Episode 9
After graciously giving his fourth slap to Robin and Ted, who couldn’t decide who should actually take the slap, and tried to pass it off on Lily and her father, Marshall’s goal to unite the group was complete, and Marshall took the fourth slap.
“Disaster Averted,” Season 7, Episode 9
In exchange for taking off the ducky tie, Barney gave Marshall three more slaps. Marshall then slapped him two more times, for the fifth and sixth slap.
“Slapsgiving 3: Slappointment in Slapmarra,” Season 9, Episode 14
After a lengthy story about how Marshall learned the “slap of a million exploding suns,” he first missed the slap, and then slapped Barney again, for the seventh time, as Boyz II Men sang “You Just Got Slapped.”
“The End of the Aisle,” Season 9, Episode 22
The final slap was delivered in a somewhat throwaway moment, when Barney saw Robin walk down the aisle. He began to freak out over his lack of cornflower blue tie, but Marshall calmed him down, with a nice, hard slap in the face.
3. The Doppelgangers
“Double Date,” Season 5, Episode 2
We’re introduced to a pair of doppelgangers: Lesbian Robin, first seen walking outside with a short haircut, baseball mitt, and flannel shirt; and Mustache Marshall, a.k.a., Hispanic lawyer Señor Justicia. Then, later on, Lily’s doppelganger, Jasmine, the Russian dancer from the Lusty Leopard.
“46 Minutes,” Season 7, Episode 14
After Lily and Marshall fled the city for Long Island, the group tried to fill out their empty booth with Stripper Lily and her boyfriend, but visits to strip clubs and winning underground poker games aren’t enough.
“Gary Blauman,” Season 9, Episode 21
We found out the fate of Jasmine, Lily’s doppelganger: she got her happily ever after with Lily’s high school boyfriend, Scooter.
4. The Interventions
“Intervention,” Season 4, Episode 4
“Right Place, Right Time,” Season 4, Episode 22
“Oh Honey,” Season 6, Episode 15
Ted initiated an intervention for himself over his feelings for Zoey, whom he thought was still married.
“The Over-Correction,” Season 8, Episode 10
An intervention Robin asked the gang to hold for Barney was instead for her because of her obsession with Barney and his new relationship with her co-worker Patrice. Little did she know…
5. Lily’s Robin Lust (which hopefully is a call back to her character on Buffy)
“Best Prom Ever,” Season 1, Episode 20
After Lily freaked out over all the things she hadn’t experienced yet before marrying Marshall, Robin kissed Lily to check lesbian experience off the list.
“Do I Know You,” Season 4, Episode 1
“I’m not going to pretend that I haven’t noticed her body,” Lily said while trying to convince Barney to confess his feelings to Robin.
“Robin 101,” Season 5, Episode 3
Lily mentioned that Robin guest-starred in confusing dreams.
“The Perfect Cocktail,” Season 6, Episode 22
While trying to figure out what drinks would make Barney and Marshall reconcile, Lily eagerly suggested drinking martinis, which Robin nixed, because they always result in Lily trying to make out with her.
“The Rebound Girl,” Season 7, Episode 11
A mix of pregnancy hormones and regular hormones made Lily have sex dreams with Robin again.
“Bass Player Wanted,” Season 9, Episode 13
Robin and Lily telepathically talked, as Andrew Rannells’ Darren hits on them, about a threesome that turned into a twosome.
“Rally,” Season 9, Episode 18
This time, Robin initiated the kiss with Lily in an attempt to wake Barney up from his extremely hungover state. It cured Lily of her attraction, but left Robin wanting more.
Nadia Chaudhury stalked her doppelganger on Yale’s campus once.