In a pinch what will work with out getting the attention of the fire dept or using tools that could end up burning your own flesh is a tea kettle. Put your kettle onto boil and once steam begins to come out and the kettle whistles place the piece of plastic in question in the path of the steam, wear your kitchen mitts for this part, wait a few minutes (no more than 3). Not only will you have warping effects like plasma would have on real metal you will have a very easy to bend and mold section of plastic. Shape it into whatever form you want then let it cool. The over all effect will very much look like something got hit with a super hot ball of energy ie plasma.