Here's why we don't think Professor Frink is exactly Jewish:
Yes, he is based on Jerry Lewis, but, more specifically, he is based on Lewis' character, Julius Kelp, in "The Nutty Professor". While we can have a lengthy discussion about the Jewishness of Kelp, it's not obvious.
His name is John Frink, Jr. As we know, Jews very rarely name children after themselves.
His middle(?) name, Nerdelbaum, seem to hint at possible Jewish roots. But the "baum" suffix is not necessarily Jewish. Could he have a goyishe father (Frink) and a Jewish mother (Nerdelbaum)? Perhaps.
In one episode, Jerry Lewis lends his voice to Frink's father. But that episode is a Halloween special and is not considered canon.
Frink is an insectivore. Jews that keep kosher don't eat insects (except for that delicious locust!) Of course, not all Jews keep kosher.
Frink appears in church scenes.
Yep, that last one pretty much settles it.