Through its successful nine-season run, CBS sitcom How I Met Your Mother saw its share of guest and recurring stars, from Wayne Brady, who played Barney’s half-brother James, to Jennifer Morrison who played Ted’s once-girlfriend Zoey, to many others. James Van Der Beek played Robin’s high school boyfriend from Canada, Jennifer Lopez a girl Barney meets at the bar, and more. But among the many actors who appeared on the hilarious series, which followed the life of Ted Mosby who, in the year 2030, was telling his teenage kids the story of how he met their mother, there are lots of other guest stars. They have played girlfriends and boyfriends, family members, co-workers, and others who crossed paths with Ted, Barney, Marshall, Robin, and Lily.

Here are 10 well-known actors that you probably forgot appeared in guest roles on the series, once upon a time.

Britney Spears

Sure, she’s more of a pop star than an actress, but Spears has done some acting in her time, too. And that included a cameo as Abby in two episodes back in 2008, during a time when she was on top of her game in the music industry. She played the receptionist at the dermatology clinic where Ted’s eventual girlfriend Stella worked.

Naïve and sensitive, she had a huge crush on Ted, but ended up sleeping with Barney. She then proceeded to mess with Barney when he didn’t call her after their tryst. Her appearance was during the same year that the mega pop star released her sixth studio album Circus that included a ton of comeback tunes like “Womanizer,” “Circus,” and “If U Seek Amy.”

Chris Elliott

This comedian was in 12 episodes from 2009-2014 as Mickey, Lily’s father who was pursuing his dream of making the next great board game. Estranged for a time with a strained relationship with his daughter, he often appeared trying to prove to Lily that he had changed. She eventually forgave him.

Concurrent to his time on the show, Elliott also appeared in the series Eagleheart, and went on to make guest appearances on a number of TV series, including Community, Hot in Cleveland, The Good Wife, and Nurse Jackie. He had a role on Law & Order: Special Victims Unit from 2008-2015, and most recently, was in Schitt’s Creek.

Kal Penn

You likely know Penn from his popular Harold & Kumar film series as well as his role in House followed by a stint working for the Obama administration when he took a break from acting. He was most recently on the political drama Designated Survivor and now stars on the NBC sitcom Sunnyside.

But from 2011 to 2014, he appeared in 10 episodes of HIMYM as Kevin, Robin’s court-ordered therapist and later serious boyfriend. He eventually proposed, but they ultimately broke up when Robin told him she didn’t want to have kids.

Sherri Shepherd

You might not have forgotten about this one yet since she appeared in the final season of the series. But Shepherd played Daphne in eight episodes in 2013, a woman who Marshall ran into on his journey back to New York from Minnesota.

They first annoy one another, then start to bond as they get are forced to work together to find a way back due to unforeseen circumstances. The role wasn’t the most memorable, and it was part of a bizarre storyline through the final season. That said, this might very well be why you’ve forgotten about it already. She is best known for serving as a co-host on daytime talk show The View from 2007-2014, and today, she hosts the game show Best Ever Trivia Show.

Bob Odenkirk

Yes, Saul Goodman himself, Odenkirk, was in How I Met Your Mother. Don’t remember? He was actually in eight episodes from 2008 to 2012 playing Arthur, Marshall’s boss. Coincidentally also a lawyer, which he plays in Better Call Saul and Breaking Bad, he was an important man at Goliath National Bank.

He’s first seen in season 3 having a shouting match with Marshall, then turning up again in season 5 at GNB where he doesn’t even remember Marshall. After Marshall quit, he tried to sabotage his career. But perhaps his most memorable tie-in was his dog Tugboat who he seemed to love more than any human.

Joe Manganiello

You probably forgot that from 2006 through to 2012, Manganiello was in this series. He played Brad, an old Columbia Law School friend of Marshall’s. Brad hosted a party that Marshall and Barney attended, then later spent time with Marshall when he broke up with Lily doing activities they used to do with their respective girlfriends, like attending Broadway shows and going for brunch.

From 2010 to 2014, Manganiello also appeared on True Blood, but he has become best known for his 2012 role in Magic Mike and 2015’s Magic Mike XXL.

Alan Thicke

From 2008-2013, the late actor was in five episodes, playing himself with a tie to Robin: he worked with her back in Canada when she was a pop star known as Robin Sparkles. He met the entire gang and revealed that he was also on an awful variety show with Robin back in the day. Any time an episode included some kind of callback to Robin’s Canadian roots, Thicke, a Canadian actor as well, had a small cameo.

Sadly, Thicke, who was best known as the patriarch on the sitcom Growing Pains, passed away in 2016.

John Lithgow

You might have forgotten that Barney’s biological father Jerry was played by none other than John Lithgow. He appeared in four episodes from 2011 to 2014 as Barney finally discovered that the man he thought was his uncle was actually his dad. And, more importantly, that his real father was not, as he was led to believe as a child, Bob Barker.

A prolific film and television actor, Lithgow has had an illustrious career that began long before this small role and continued well after. His most notable roles include 3rd Rock from the Sun, prior to HIMYM, as well as the menacing serial killer Arthur Mitchell in Dexter (also prior to this role) and as Sir Winston Churchill in the first season of The Crown.

Martin Short

This iconic comedian appeared in three episodes in 2011 and 2012 as Garrison, a senior partner of the firm where Marshall worked. Equally passionate about saving the world by saving the environment as Marshall, Garrison was funny but also pessimistic. It’s Short’s character, in fact, who bursts into flames in a beekeeper suit during the episode with Marshall and Lily’s housewarming party.

Short, of course, is best known for SCTV, Saturday Night Live, and a long string of movies dating back to the ‘80s, including cult classics like Mars Attacks! and Three Amigos. He can most recently be seen in a small role in Apple TV+ series The Morning Show.

Danica McKellar

Winnie Cooper herself, McKellar, who is best known for The Wonder Years, was on the show, too. It was during the early years, from 2005-2007, when she was in two episodes as Trudy, one of Ted’s many one-night stands. Her first appearance was in the episode that sparked a long-running gag and mystery called The Pineapple Incident.

McKellar has done plenty of work since then, including on the Netflix series Project MC2, as well as several television movies on Hallmark Channel. She has also written several books geared at getting young girls interested in math and science.