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Why Dr. Kevin Campbell From The Big Bang Theory Looks So Familiar

The main characters in "The Big Bang Theory" are a notoriously brainy bunch, if not always the most emotionally or socially intelligent. Sheldon (Jim Parsons) is a theoretical physicist who earned his Ph.D. at 16; Leonard (Johnny Galecki) is an experimental physicist; Raj (Kunal Nayyar) is an astrophysicist; Howard (Simon Helberg) is an aerospace engineer who spends some time in space. Howard and Sheldon's respective partners — Bernadette (Melissa Rauch) and Amy (Mayim Bialik) — are also experts in their respective biological fields.

Over the course of the sitcom's 12-season run, the "Big Bang Theory" gang rubs elbows with other scientists both fictional (Lewis Black's entomologist, for example) and real (Stephen Hawking and Brian Greene make appearances, among others). In the show's final season, viewers are introduced to Dr. Greg Pemberton and Dr. Kevin Campbell, two Fermi-Lab physicists angling for a Nobel Prize. The pair prove to be as dysfunctional and conniving as they are intelligent, and Sheldon and Amy walk away with the prize. Here's why the actor who plays Dr. Campbell looks so familiar.

Kal Penn jonesed for burgers in Harold & Kumar Go To White Castle

Dr. Kevin Campbell is played by Kal Penn, who has been working in Hollywood since the late 1990s. After appearing in shows like "Buffy the Vampire Slayer" and "ER," Penn landed the part of Taj Mahal Badalandabad in "National Lampoon's Van Wilder," a role he would reprise in 2006's "Van Wilder: The Rise of Taj" (via IMDb).

In 2004, Penn starred as Kumar alongside John Cho's Harold in the buddy comedy "Harold & Kumar Go To White Castle." A tale of self-actualization (fulfilled, in part, by hamburgers) cloaked by clouds of marijuana smoke, "Harold & Kumar Go To White Castle" is also notable for subverting common stereotypes. "The older people around Hollywood, the older people in town were like, 'We don't know if America is ready for two Asian American men as leads in a comedy,'" Penn told E! News. For him, the film is much more than just a stoner comedy. "When you don't see yourself on screen, it limits your view of what might be possible in your own life," he said. "And there might be exceptions to that but...it's incredible that something like this exists." He reprised the role in the 2008 and 2011 sequels.

Penn starred in The Namesake

Following "Harold & Kumar Go To White Castle," Penn appeared in a number of small roles across genres, including "Son of the Mask" and in the romantic comedy "A Lot Like Love." "Harold and Kumar" helped Penn land the leading role in "The Namesake," his biggest and most dramatic part to date, in part because director Mira Nair's son had seen the actor in the stoner comedy.

Based on Jhumpa Lahiri's novel of the same name, "The Namesake" follows Gogol Ganguli, the son of immigrants from West Bengal, whose unusual name shapes his upbringing as a first-generation American. For Penn, playing Gogol was a deeply personal experience. "Gogol's internal struggles to find his true identity spoke to me, very deeply and very immediately," Penn said (via Emanuel Levy). "One of the things I really like about this story is that it dispels the myth that being a young American looks a particular way or has a particular tradition."

He played Dr. Lawrence Kutner on House

Alongside his burgeoning film career, Penn landed a number of television appearances as well, including a four-episode arc in "24." In 2007, he joined the cast of "House" as Dr. Lawrence Kutner, a member of House's (Hugh Laurie) diagnostic team alongside Dr. Remy "Thirteen" Hadley (Olivia Wilde) and Dr. Chris Taub (Peter Jacobson). After two seasons on the medical drama, Kutner abruptly ends his own life.

Behind the scenes, Penn decided to leave the series to take a job as the principal associate editor in the White House Office of Public Engagement. At the time, Penn told creator David Shore, "I'm having an incredible time, but there's something aching in me to do something completely different and take a break from the acting thing for a while" (via EW). Penn served in his post under the Obama administration from 2009 to 2011, whereupon he returned to acting.

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Penn analyzed the gang in How I Met Your Mother

Penn followed up his White House gig with a recurring role in "How I Met Your Mother," reuniting the actor with his "Harold & Kumar" co-star Neil Patrick Harris. Penn plays Kevin, Robin's (Cobie Smulders) Season 7 love interest who works as a court-appointed therapist. While Kevin spends his days counseling mentally unfit felons, he's in no way prepared to handle the analysis that the "How I Met Your Mother" friends require. In one episode, he snaps and lambasts the gang's dysfunctional co-dependent dynamic.

Penn, a longtime fan of "How I Met Your Mother," was thrilled to join the series, even if it was just for 10 episodes. "I love the show, so it was perfect," Penn told TV Guide in 2011. "I had also worked with Alyson [Hannigan] briefly, like way back in the day I did an episode of 'Buffy the Vampire Slayer' and she was great to work with ... I said I would love to do it if they would like to have me." While Penn mostly appeared in Season 7, he returned for a Season 9 episode, where it was revealed he was dating Jeanette (Abby Elliott).

Penn used his White House experience in Designated Survivor

In 2016, Penn began playing Seth Wright, a White House speechwriter, on the ABC drama "Designated Survivor." When a terrorist attack kills the president and the major figures in the line of succession, Secretary of Housing and Urban Development Tom Kirkman (Kiefer Sutherland) is suddenly sworn in, and Wright is promoted to press secretary.

In addition to acting on the show for three seasons, Penn was able to bring his bureaucratic credentials to the series and acted as a consultant (via Deadline). Still, the actor tried to not be a stickler for accuracy on set. "I feel like I'm always the annoying one," Penn said in an appearance on "Jimmy Kimmel Live." "The Oval Office is to scale and [the crew has] done a great job replicating it. All the other rooms are in the wrong place, sometimes you'll get lost." Penn added, "Part of not correcting them is letting them go crazy with the fiction, which is probably what people want to see, instead of the accuracy."