I don't believe this is actually a Tuba. Tubas, even in 3/4 size, are typically too large to hold in one's hands in the manner depicted. What the actor is more likely holding is a Baritone (or, more properly, Euphonium).
Unless it has been confirmed by the producers of the show that this instrument is indeed a Tuba, this page should be edited. For further information, please reference http://en.wikipedia.org/wiki/Euphonium. Tha crock85 10:17, January 3, 2010 (UTC)