If a squirrel bites you, is it just funny or a threat to your health?

Can be dangerous. Bites from wild animals such as squirrels can be dangerous. Although the risk of rabies and tetanus is low these wounds can easily become infected. A squirrel bite should be cleaned well and should be evaluated by a physician.
Not funny. No bites from squirrels have been documented to transmit rabies to humans in the us. The wound should be cleansed and tetanus status needs to be assessed. According to j.P. Wyatt, normally prophylactic antibiotics are not required unless there is involvement of deep structures.