A penny inside a Wii is extremely unlikely. The disc slot is a narrow, motorized feeder (≈13 mm tall) leading directly to the optical drive. A standard penny (1.52 mm thick, 19.05 mm diameter) cannot enter the slot vertically and would jam the mechanism horizontally.
If console feels hot / fan loud / shuts down:
If the console works fine, there is no penny. Check the SD and GC slots — that's where coins actually go.