Wibbly lever

The Wibbly Lever is a TARDIS component. It is used to control the implosion of the TARDIS in the 2011 red-nose special "Time". The TARDIS had materialized inside itself. The Doctor was trying to figure out which lever to use to implode the TARDIS and the wrong one would kill everyone inside the TARDIS. He (from the future) suddenly ran in and shouted "The Wibbly Lever!" The Doctor promptly threw the lever and ran into the exterior to tell his past self which lever.