Sir Ian McKellen's episode of Doctor Who was The Snowmen, broadcast Christmas Day 2012. He played The Great Intelligence, appearing in voice only.
Ash says he loves spending time with O.A.P.s, which disconcerts Freddy. You had to be over 65 years old to collect Old Age Pension.
Stuart says he didn't know Graham Norton was gay. The gag is that Norton, an Irish comic and BBC TV personality and show host, was famous for his openly gay sexual double entendres and flamboyant behavior.
Stuart teases Freddie about being on one episode of Dr. Who. Ian McKellen and Derek Jacobi both were on one episode each of Dr. Who, though Ian McKellen appeared on his in voice only.
Much ado is made of their dog being 20 years old. Dog lifespans vary enormously with breed. A Great Dane rarely lives past 8 years while an 18 year old Yorkshire Terrier is not that remarkable.