How We Met These Memorable HIMYM Guest Stars

Perry plays a character so naive that the gang can only remember her as "Honey" — as in a patronizing "Oh, honey." But she's a sweetheart, and she comforts Barney while he's dealing with his mixed emotions over his biological father.

Jennifer Morrison stars as one of Ted's girlfriends, Zoey Pierson. She's an activist who vehemently opposes Ted's job of tearing down The Arcadian to build a new skyscraper, and eventually their differing views lead to a breakup.

Remember when Barney thinks The Price Is Right host Bob Barker is his real father? He's not, but that episode is amazing.

Country star Carrie Underwood moonlights as pharmaceutical sales rep Tiffany, a girl who dates Ted and provides him with a valuable dating lesson as she strings him along with ease.

Sarah Chalke has a long character arc as Dr. Stella Zinman, Ted's fiancé who leaves him at the altar to reconcile with her ex-husband.

Alan Thicke plays himself as the host of Space Teens and Hoser Hut, Canadian shows that Robin appears as Robin Sparkles. Nicole Scherzinger guest stars as Jessica Glitter, Robin's former best friend.

Following her breakup with Ted at the end of season two, Robin rebounds hard — with dreamy Gael (Iglesias). Gael doesn't stick around for long, but when he is there, he excels at playing at the guitar, giving massages, and being really good-looking.

The pop star guested on the show as a receptionist named Abby at the office of Ted's dermatologist, Stella. She harbors a crush on Ted the first time she appears but then transfers her affections to Barney, whom she pretends to be dating to make Ted jealous.

Kyle MacLachlan plays George Van Smoot, better known as The Captain. He's Zoey's ex-husband and, eventually, Lily's boss.

After insisting that his dad is Bob Barker for years, Barney finally meets his real father in season six. Lithgow gets the honor of playing Jerry, and though he's not the cool, freewheeling guy he once was, he's still a warm, loving father figure (and light years away from his other infamous guest role as the Trinity Killer on Dexter).

Mandy Moore plays against type as a tattooed party girl in the third season. She's also totally not Ted's kind of girl, but he uses her to make himself feel better after breaking up with Robin.

The sultry J Lo popped up as the author of a self-help book about love (with the classic title of Of Course You're Still Single, Take a Look at Yourself, You Dumb Slut). With her hot bod and resistance to pickup lines, she becomes Barney's primary target.

Joe Manganiello appears early in the series as Brad, a friend of Marshall's. He returns years later (after his star-making turn on True Blood) to reprise his character. He goes on a botched date with Robin, then, in season eight, he goes head-to-head in the court with Marshall, using his good looks to woo the jury of women.

Saturday Night Live's Will Forte turns up in season three as Randy Wharmpess, Barney's coworker at Goliath National Bank who praises everything Barney does.

Bryan Cranston appears in season two and again in season nine as Hammond Druthers, Ted's nightmare of a boss.

Lost's Jorge Garcia plays Steve "The Blitz" Henry, who attends college with Ted and Marshall. He is famous for missing out on epic adventures and uttering, "Aw, man!" when he finds out what he missed.

Robin's hidden pop star identity comes out for the second time when James Van Der Beek played Robin Sparkles's teen idol boyfriend Simon. He goofed around with Robin in their early '90s video for "Sandcastles in the Sand," one of the best HIMYM moments of all time.

Actress and comedian Tracey Ullman guest stars in the final season as Robin's mother. Though her character is afraid of flying, she braves the skies to be at Barney and Robin's wedding.

Ashley Benson plays Carly Whittaker, Barney's younger half-sister who briefly dates Ted. He breaks up with her, realizing their interests don't really mesh.

Remember Royce (Greer)? Ted dates her after he gets left at the altar by Stella, and they go on a date to see The Wedding Bride, the infamous movie based on Ted and Stella's failed relationship.

Pretty Little Liars' Lucy Hale turns up as Robin's younger sister Katie in "First Time in New York" then appears again during the final season for Robin's wedding to Barney.

Taran Killam (Cobie Smulders's real-life husband!) turns up early as Gary Blauman, an employee at Goliath National Bank, and returns in the final season as a polarizing character who everyone seems to love or hate.

Billy Zabka comes on as a recurring guest star throughout the show's final season. He plays himself, the true hero of The Karate Kid and Barney's idol.