"Mighty Science Theater" is the official name of the song played over the end credits of almost every episode of Mystery Science Theater 3000. It is a slowed down, abbreviated instrumental version of the "MST3K Love Theme" done in synthesizers in a more majestic style. It has been part of the show since Season 1.
Once in a while, a gag from the last host segment in the show would be extended into the credit sequence. This usually resulted in sound effects or voices being played on top of "Mighty Science Theater" (such as Pearl snoring in the end credits of The Thing That Couldn't Die). On other occasions, "Mighty Science Theater" would not be played at all, and would usually be replaced with an instrumental or part of a song sung earlier in the episode, or like in the case of Manos, the chilling 'Torgo' theme plays.