Tom Selleck was “scared to death” when he guest-starred on ‘Friends.’ The 77-year-old actor joined stars Courteney Cox, Jennifer Aniston, Lisa Kudrow David Schwimmer, Matt LeBlanc and Matthew Perry on the sitcom in 1995 for a series of appearances as Dr. Richard Burke – the short-term boyfriend of Courteney’s character Monica Geller – and admitted that he was terrified about taking on the role because he had never done a comedy series. He said: “The hardest thing is to guest on a show. I try to relax the new actors because that’s really hard to come on a show where everybody’s up to speed. I w…