Knock! Knock! Who's There? (novel)

 was a book published by BBC Children's Books. Similar to The Doctor Who Fun Book, it contained activity-book-type features as well as short parodical or comedic stories.

Publisher's summary
-What do we want?

-TIME TRAVEL!

-When do we want it?

-THAT'S IRRELEVANT!

Packed with a dimensionally transcendent TARDIS-load amount of jokes, gags and riddles, this is the official Doctor Who joke book! Remember: it's funnier on the inside!

Contents

 * Doctor Who jokes