John Brown was a famous abolitionist. He was executed, and there was a question of what do with with his remains. “John Brown’s body” then became kind of a meme and was turned into a song:

As an aside, interesting note in the Wikipedia article about him:

Brown was the leading exponent of violence in the American abolitionist movement, believing it was necessary to end slavery after decades of peaceful efforts had failed.

“John Brown’s Body” was a folk song popular with the Union during the American Civil War

Unless there’s a deeper meaning that escapes me too, this one is just wordplay

I think the dog bowl is actually an oilpan, for changing oil. The hose is probably for washing cars getting said oil change.