sorry i never seen this earlier but it sounds like your pacman frog is shedding. my frogs do that all the time and shed. hes just stretching the skin off and opening his mouth and eating the skin since thats what frogs do. he should have stopped a long time ago but next time it happens you will know. if he keeps doing this i would post this in a forum more specific to frogs, such as http://www.frogforum.net/content/ that site has helped me alot with my frogs so just go there if you have a question, you will get a quicker answer there.