I was reading a book last night which said (something along the lines of) ".. and I was frog-marched down the hallway". (I can't remember the exact quote, and now I can't find it... d'oh!)

Anyone got any ideas about why the frogs were being marched, as opposed to any other animal? And how were the frogs marching? Have you ever seen a frog march? They's jumping, leaping and - at a stretch - hopping, but I ain't never seen them marching.