(as) full as a tick
Having consumed large quantities of food or drink. A reference to a tick that is engorged with blood. There was so much delicious food at the banquet that I'm just full as a tick now.
*full as a tick
very full of food or drink. (Alludes to a tick that has filled itself full of blood. See also tight as a tick. *Also: as ~.) Little Billy ate and ate until he was as full as a tick. Our cat drank the cream until he became full as a tick.