I tried a basic search on the quote, with quotation marks around it, with and without the name W.C. Fields. No luck. I don't remember ever hearing the quote, either in a movie or in conversation but it's a long, long time since I saw a movie with W.C. Fields as a member of the cast so I'm unlikely to remember the quote anyway.
When I searched the term:
movie quote "Sounds like a line from a song" W.C Fields
a couple of sites were mentioned which compile movie quotes but I didn't look at those sites. It might be worthwhile checking those out.