For those who have never seen these, this is a pair of Romper Room Romper Stompers.  Kids would put their feet over the yellow cups and hold the green plastic cords and walk around, clomping as they walked.  Sort of like in Monty Python, how they clomped the coconuts together to make horse sounds.

This is an original pair from the 1970s with the original plastic cords.  See pictures for more details.