Anyway, this is the one where there's a world of fictional characters because there's some powerful aliens who want to take over Earth by making real people fictional so they can control them...I think. Don't ask me to explain it in too much detail. It will make your head hot.
Cool things: the unicorn looked pretty good; Medusa made use of stop motion animation; Lemuel Gulliver's lines all come from the written novel. They were smart enough to avoid showing the Minotaur, using its scary shadow instead.
I was mildly amused by the version of Rapunzel, who had fake eyelashes and hopefully asked everyone, "Are you a prince?" Alas, she is the only female fictional character we see, aside from some girls in a crowd of children.
My goodness, Zoe's sparkly catsuit. The bit in which she and Jamie are clinging to the TARDIS console while it revolves in space...there's an impressive back view of that costume. Hamish Wilson wasn't bad as Jamie, but I noticed he wasn't as physical--Frazer Hines as Jamie is always grabbing or hanging on to the others, either protectively or in search of protection.
The Karkus, a superstrong superhero of the future (Zoe used to read his adventures in a comic strip) is a trip. He has a strange and geographically untraceable accent, vaguely German, which somehow suits him.
More on this episode, and also more here. Here's The BBC episode guide.