It was confirmed at the weekend that Walliams will play a character called Gibbis in an episode written by Being Human creator Toby Whithouse.
Smith told The Daily Star: “David and I started filming on the episode last week and he is great. He just makes me laugh all the time. He is terribly funny and I am very fond of him.”
He continued: “I haven’t asked him to do any of the Little Britain voices just yet, but I have been asking him lots about that show and Come Fly With Me. I know he is going to be very funny in Doctor Who.”
Smith also spoke about his future with the show beyond Series 6, saying: “I certainly hope to be back. Steven Moffat has just told me the title of the 2011 Christmas special and I nearly fell off my chair!”