When Foreman and House are discussing Foreman's sabotaged interview, House suggests it was Ashton Kutcher. In season 1's "Poison", one of the clinic patients (an 82-year-old woman with a recurrence of syphilis) says that House reminds her of Kutcher, to which House replies "People are always mixing us up."
As Dr. House and Dr. Eric Foreman talk in an elevator about who sabotaged Dr. Foreman's interview, Dr. House says "maybe it was Ashton Kutcher," whose character in That '70s Show (1998) Kelso, was friends with Topher Grace's character of the same name as Dr. Eric Foreman.
When Foreman accuses House of canceling his interview, House replies "Maybe it was Ashton Kutcher". Ashton Kutcher is the host of _Punk'd_ where he and his crew play pranks on celebrities in each episode.