The Most Gigantic Lying Mouth of All Time is a DVD released on December 1st 2004 that compiles four episodes of a program of the same name broadcast on the band's website, Radiohead.TV, to promote their album Hail to the Thief. Episodes contain music videos, snippets from the album's recording sessions, and other bizarre interludes.

Every episode opens with a deliberately cheesy intro set to 'The Most Gigantic Theme' by Tim Bran, which is a blatant pastiche of 'Spanish Flea' as performed by Herb Alpert and the Tijuana Brass. This is soon interrupted by a snippet of 'Momentum'.

Each episode is hosted by Chieftan Mews, a character described by the band as 'not of this world'. He is portrayed by the band's longtime producer, Nigel Godrich.