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NEIL PATRICK HARRIS: SPINNING THE BIG WHEEL WITH BOB BARKER
''Showdown,'' season 2, episode 20
Harris lived out a personal fantasy while exploring Barney's slightly cuckoo delusions about his birth father — namely, that he is the secret love child of Bob Barker. Barney's quest took the whole show to the Price Is Right set shortly before Barker's retirement, much to Harris' delight. ''I've watched The Price Is Right since I was a wee tot,'' Harris explains, ''and I always dreamt one day I would be on the show. But then suddenly I was an actor on TV [with Doogie Howser, M.D.], and you can't be on The Price Is Right if you're on TV. So we finally accomplished my goal.''
2 of 10
JOSH RADNOR: ROAD TRIPPING
''Dual Citizenship,'' season 5, episode 5
''I really like when Marshall and Ted hop in the car and travel distances,'' says Radnor, citing the current season's trip to get one last slice of pizza at a filthy dive named Gazola's in Chicago as one of his faves. ''For some reason I feel free as an actor when we're in that car being goofy. I like it when Ted gets kind of psycho nostalgic, and wants to hit these old spots and memories. He's clearly never lost that nostalgia, because he's spending one really long afternoon telling his kids every story that ever happened to him in this 8-to-12 year period. Those poor children.''
3 of 10
ALYSON HANNIGAN: BEING SERENADED BY THE USC MARCHING BAND
''Three Days of Snow,'' season 4, episode 13
''My absolute favorite [moment] is when the USC Marching Band played for me in the episode when Marshall and Lily are meeting each other at the airport,'' says Hannigan, who loves scenes exploring Marshall and Lily's relationship. ''I was very pregnant, and even if I weren't pregnant, that was just such a touching moment. But to be hormonal, and to be serenaded with all of those beautiful musical people — I was bawling. And I wasn't the only one.''
4 of 10
COBIE SMULDERS: THE 'SANDCASTLES IN THE SAND' VIDEO SHOOT
''Sandcastles in the Sand,'' season 3, episode 16
Smulders loves both of her Robin Sparkles videos, but gives ''Sandcastles'' the edge over ''Let's Go to the Mall'' because of the ''cinematic'' nature of shooting at Zuma Beach in Malibu. ''That was such a beautiful frikkin' day,'' she says. ''I remember getting up and it was dark out, crawling out of bed, getting in my car, and going much further in Malibu than I thought it was gonna be. And then I go and get makeup and this wig in this little rinky-dink trailer, and when I opened the door, the sun was rising on the beach. There were dolphins in the water, and seals everywhere. Just seeing all of our crew out there — it was magical.''
5 of 10
JASON SEGEL: WORKING WITH CHRIS ELLIOTT
''Slapsgiving 2: Revenge of the Slap,'' season 5, episode 9
When Elliott appeared as Lily's dad — a failed board game inventor — it gave Segel a chance to appear with one of his comedic heroes. ''Get a Life was like The Simpsons for me and my friends,'' Segel says. ''It had such a strange tone and sense of humor. When you see someone doing something different from the mainstream and being so funny, it's pretty inspiring. He's the man.'' Segel's favorite part of the episode? Watching Elliott's feigned joy every time he presented one of his new (and increasingly horrible) games. ''He has that thing I try to do in my acting, which is every once in a while, to revert back to total childhood wonder.''
6 of 10
NEIL PATRICK HARRIS: PLAYING BARNEY AS A HIPPIE
''Game Night,'' season 1, episode 15
In the second half of season 1, we learned the dark secret behind Barney's suave persona: Before heartbreak turned him into a womanizer, he was once a tie-dye-wearing, goatee-sporting hippie. ''That was the first time we'd actually seen the other side of Barney,'' says Harris. ''I got to look as sad and granola as possible. And sing at an awkward Casio keyboard and cry. That made me happy.'' Harris, however, does not agree with the suggestion that his hippie incarnation looked kinda smelly. ''If you think patchouli smells bad,'' he huffs, ''shame on you.''
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JASON SEGEL: WORKING WITH BOB ODENKIRK
''The Chain of Screaming,'' season 3, episode 15
Segel had the pleasure of being reamed out by another of his heroes, when Mr. Show's Odenkirk guest-starred as Marshall's boss. (They shared more scenes in this season's ''Last Cigarette Ever.'') ''He's so gracious,'' says Segel. ''He just loves performing. And he has this intellectual approach to it that I admire. He really thinks about how a joke works best.'' Segel says both Odenkirk and Elliott pushed him to step up his game as an actor. ''I don't always feel that way — not that I feel like I can phone it in — but when you really want someone to respect what you do, it forces you to be your best.''
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ALYSON HANNIGAN: CHASING THE COCKAMOUSE
''Matchmaker,'' season 1, episode 7
Hannigan's favorite not-quite-on-screen moment came in the first season, as Marshall, Lily, and Robin attempted to exterminate the terrifying ''cockamouse'' (possibly a mouse, possibly a cockroach) from the apartment. ''I remember Cobie and Jason and I all having to run to the window,'' says Hannigan. ''It was really slippery, and Cobie couldn't open the window, and at some point, somehow — I don't even know logistically how it happened — we were all three on top of each other like a sandwich. It was just the most fun!''
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JOSH RADNOR: COLLEGE FLASHBACKS
Radnor favors any and all looks back at the gang during their college years. ''There's something about Ted's college persona that really amuses me,'' he says. ''He was pathetic, but he was oblivious to his patheticness, which makes it okay, I think. I like the wig. I like the spectacles. There's also something funny in plundering the '90s, making them seem like a period piece. I like how the show is creating its own lore, and rewards faithful viewers with callbacks to things.''
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COBIE SMULDERS: DANCING IN SUITS
For the 100th episode, airing Jan. 11
For the upcoming milestone, the cast suited up for a musical number called ''Nothing Suits Me Like a Suit'' alongside 65 dancers on the Fox lot's New York Street set. Smulders was in heaven. ''There's something old-showbiz about watching the dancers rehearse and making sure everyone's in the right wardrobe,'' she says. ''I think it just goes back to a time when everyone had to sing, dance, and act. I love that era. I love anything that has to do with dancing. And Carter [Bays] and Craig [Thomas, the show's co-creators] always write such good music.''