Mr Tickle

Mr Tickle was a fictional character with his own series of books.

Bernice Summerfield made a mental note to herself once: "Dear diary, I'm not writing this down – if I could I'd be Mr Tickle – so I'm going to have to memorize this, or paint it on the walls." (PROSE: Falls the Shadow)

The Tenth Doctor asked Rose Tyler if she wanted to meet Mr Tickle, but then decided that he might be annoying since he lived in a universe of nominative determinism. (AUDIO: Infamy of the Zaross)

When Anya Kingdom protested that the Tenth Doctor had called her into an dangerous environment just to hold a switch, the Doctor defended that the process had to be simultaneous and he was not "made of arms" like Mr. Tickle only for her to not get the reference. (AUDIO: The Wrong Woman)

Behind the scenes
Mr. Tickle was the titular protagonist in the very first Mr. Men book by Roger Hargreaves, published in 1971.

The inspiration for this character came from a question by Hargreave's 8-year-old son, Adam Hargreaves, who himself would go on to write all fourteen books for Dr. Men, a Doctor Who spin on the iconic children's series, beginning in 2017.

While never specified as his, arms that looked like Mr Tickle's once tickled the Doctor. (NOTVALID: The Daft Dimension)