The anything slide was a helter skelter that could be found in a room in the Doctor's TARDIS by his Eleventh incarnation. One would shout out whatever they wanted as they went down the slide, and the TARDIS' telepathic circuits tuned into what was said and materialise a big heap of it at the bottom.
The Doctor allowed Amy Pond and Rory Williams to use the slide; after the Doctor demonstrated its capabilities by wishing for a pile of jelly babies, Amy went down the slide wishing for chocolate, while Rory, having fun on the slide, simply shouted "Wheeeeee!" all the way down... (PROSE: Knock! Knock! Who's There? [+]Error: Code 2 - no data stored in variables, cache or SMW.)