It might be amusing to ask which animal has the largest ears for the size of its head:
Townsend's big-eared bat (the winner):
Might be fun to mention that the largest ears overall (elephant) have the least to do with actual hearing. Their size is almost completely due to their function as cooling fins.
If you double the height of an animal, its volume goes up eightfold (2^3), which means that it generates eight times the amount of heat. However, its surface area only goes up fourfold (2^2), so there is proportionally far less surface from which to evaporate moisture, and therefore get cooler. Therefor large animals have to either spend a lot of time in the shade, or else have large appendages with lots of surface veins. So to speak.