Breckin Erin Meyer (born May 7, 1974) is an American actor, voice actor, comedian, writer, producer and drummer known for roles in films such as "Clueless", "Road Trip", "Rat Race" and the "" film series.
Knocked Up is a 2007 American romantic comedy film written, directed, and co-produced by Judd Apatow, and starring Seth Rogen, Katherine Heigl, Paul Rudd, and Leslie Mann.
 It follows the repercussions of a drunken one-night stand between a slacker and a just-promoted media personality that results in an unintended pregnancy.
Jeremy Merton Sisto (born October 6, 1974) is an American actor, producer, and writer.
 Sisto has had recurring roles as Billy Chenowith on the HBO series "Six Feet Under" (2001–05), and as NYPD Detective Cyrus Lupo on NBC's drama series "Law & Order" (2008–10).
 He also starred in the comedy "Clueless" (1995), the biblical miniseries "Jesus" (1999), the drama "Thirteen" (2003), and the horror film "Wrong Turn" (2003).
 In 2004, he starred as bigoted baseball player Shane Mungitt in "Take Me Out", for which he was nominated for a Los Angeles Drama Critics Circle Award for Featured Performance in a Play.
 In 2006, he starred in the play "Festen" on Broadway.
Shehzad Sheikh or Shahzad Sheikh is a Pakistani film and television actor and model, known for playing the lead role in the 2015 film "Karachi Se Lahore".
 He also starred in the series "Annie Ki Ayegi Baraat", "Mi Raqsam", and "Mere Hamrahi", and a TV film "Main Kukkoo Aur woh".
 He is the son of well-known actor Javed Sheikh.
Donald Adeosun Faison ( ; born June 22, 1974) is an American actor, comedian, and voice actor, best known for his leading role as Dr. Chris Turk in the ABC (formerly NBC) comedy-drama "Scrubs" (2001–2010), and a minor role as Murray in the film "Clueless" (1995) (subsequently reprised in the television series of the same name).
 He also starred as Phil Chase in the TV Land sitcom "The Exes" (2011–2015).
Alicia Silverstone ( ; born October 4, 1976) is an American actress.
 She made her film debut in "The Crush" (1993), earning the 1994 MTV Movie Award for Best Breakthrough Performance, and gained further prominence as a teen idol when she appeared at the age of 16 in the music video for Aerosmith's "Cryin'".
 She starred in the comedy hit "Clueless" (1995), which earned her a multimillion-dollar deal with Columbia Pictures, and in the big-budget film "Batman & Robin" (1997), playing Batgirl.
 She has continued to act in film and television and on stage.
 For her role in the short-lived drama comedy "Miss Match" (2003), Silverstone received a Golden Globe Award nomination for Best Actress – Television Series Musical or Comedy.
 A vegan, Silverstone has endorsed PETA activities and has published two nutrition books.
Paul Stephen Rudd (born April 6, 1969) is an American actor, comedian, writer, and producer.
 He studied theatre at the University of Kansas and the British American Drama Academy, before making his acting debut in 1992 with NBC's drama series "Sisters".
 He is known for his starring roles in the film "The Cider House Rules" (1999), "" (1995), and the comedy films "Clueless" (1995), "Wet Hot American Summer" (2001), "" (2004), "The 40-Year-Old Virgin" (2005), "Knocked Up" (2007), "Role Models" (2008), "I Love You, Man" (2009), "Dinner for Schmucks" (2010), "Our Idiot Brother" (2011), "Wanderlust" (2012), "This Is 40" (2012), and "" (2013), and for playing the superhero Ant-Man in Marvel Studios' "Ant-Man" (2015) and "" (2016).
Elisa Donovan (born Lisa Adaline Donovan; February 3, 1971) is an American actress, writer, and producer.
 She is most recognized as the character Amber from the 1995 film "Clueless", in which she starred opposite Alicia Silverstone.
 She would reprise the role for the 1996-99 TV series of the same name, with Rachel Blanchard taking over Silverstone's role.
 She also starred in six films in the acclaimed "The Dog Who Saved" saga.
"R U Professional" is a 2009 satirical song by the American indie rock band The Mae Shi, inspired by a July 2008 outburst by actor Christian Bale on the set of "Terminator Salvation".
 Bale was filming with actress Bryce Dallas Howard when he berated director of photography, Shane Hurlbut, for walking into his line of sight.
 An audio recording of the incident appeared on website TMZ on February 2, 2009.
 The Mae Shi composed and recorded the song later in the same day, and released it the next day.
 The group stated that the piece was created to honor Bale.
 The song parodies Bale by sampling his voice from the 2008 diatribe.
 The chorus incorporates Bale's use of the word "professional" from his flare-up.
 The lyrics reference several films the actor starred in, including "Newsies", "Swing Kids", "American Psycho", and "The Dark Knight".
Justin Walker is an American actor best known for his portrayal of Christian Stovitz in the 1995 comedy film "Clueless".

Question: What actor starred in Knocked Up and Clueless?
Answer: Paul Rudd