Even Greener Pastures

In Irish snag is a kind of bird (snag breac "speckled snag" is a magpie, snag darach "snag of-oak" is a woodpecker), but if you have a snag on you, it means you have hiccups (incidentally, snagcheol "snag-music" means "jazz").
If you have a muc (pig) on your brow, then you're scowling.
If a daol (beetle) hits you, you get a sudden urge to do something.
A cearc (hen) in your armpit is a bubo or swollen lymph node, but if someone has tinneas na circe ("the hen's sickness") then they're just fidgety.
If you have a cuil (fly) on you, then you're in an angry mood.
If you have a spideog (robin) on your nose, then you need a tissue.
If you have gliomóga (lobsters) on your eyes, it means your eyes are popping out of your head.

In English you can also have a frog in your throat [be hoarse], a flea in your ear [having been sternly rebuked] or a monkey on your back [be addicted to something].