"Stuart" is the name of a song (or more accurately a skit with musical backing) by The Dead Milkmen. It was released on their album Beelzebubba, and is 2 minutes long, which is fairly long for a Dead Milkmen song.
The song, such as it is, is a long rambling rant by an older man towards a teenage boy, detailing a plot between homosexuals and Martians to invade the earth. Stuart is the recipient of this information because "he isn't like the other people, here in the trailer park". In fact the entire first verse (such as it is) of the song lays this out by detailing the unrelated story of a boy who was so stupid that he looked for his pet burrow owl in a tree.
The song has something of a cult status, and like many Dead Milkmen songs, is an in-joke among the initiated. Inside of the song's absurd 2 minutes, there is actually a series of intricate comments on American society.