The Buster cube does not have a "plug" in it. I have tried to remove the filling mechanism and have not succeeded. I even tried a pair of vice grips! There are some cheap knock offs out there. It was probably one of them. Barb Bowes, NJ down at the shore! Bo, Molly, Chelsea & Flopsy the Pyr Shep The more people I meet, the more I like my dog! bamb@monmouth.com