Of course it's silly, it's a kids' song. As I understand it, it was written after watching his kids playing sailor using an old shutter as the ship, with assorted other kidlike props.

We do enjoy the song, always have, but seldom sing the last three verses - it makes the song awfully long, and they're REALLY silly.

And for Kendall and 'cleese, 50 choruses of "On top of Spaghetti."