My name is***** and I'm here to help you.
My goodness, Petey certainly gets into trouble.
I assume that he either vomited or passed the styrofoam.
Clumping litter usually dissolves when wet. So we would expect him to pass it. However if he ate a large amount he could get an obstruction.
How long ago did he eat the litter?
There is also the possibility that he ate something else and he could be in trouble.
You should take Petey to your vet as soon as possible to be examined. He/she would feel Petey's abdomen to check for impaction. He might need an xray to be sure.
In the meantime, keep a keen eye on Petey to prevent him from eating anything else.
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Good luck to you and Petey. And Happy Holidays!