Based on the comments and emails I've received there appear to be some issues with the Diamond Select Cthulhu bank Raven reviewed yesterday. In a number of cases the bottom of the piece is warped, making the bank wobbly or locking in the coin plug.
I'm still waiting for the one I ordered to arrive, but based on my experience with vinyl model kits I would suggest using heat to soften the vinyl on the bottom of the idol. The easiest way is to use a tray of hot water. Not boiling, mind you, but hot enough to be uncomfortable, not painful, if you put your hand in it. Hold the bottom of the bank in the hot water for a minute or two and the vinyl should soften right up. That should allow any stuck plugs to be twisted out. For the warping issue, grab the flange on the plug and pull until the bottom is level, then rinse the vinyl with cold water to set it.