One verse that I learned that has appeared here only as a slight variant is this:

Ding-dong, Ding-dong
Funeral bells on a September morn
Rose's roses are dead and gone, sire
Dead and gone

Also, I don't know if this was from another song and my friends just threw it in there, but after the verse with the moss-covered stone, we would sing:

The wind in the willows blows like a solitary song
The wind in the willows blows like a solitary so-o-ong