I heard it first on "The Dick Van Dyke Show", and then later on "That Girl", just as Jim Dixon noted. I assumed (without any actual knowledge) that it was an old vaudeville song.

Working strictly from the memory of hearing it on those two shows, I have it as

I'm in love, I'm in love
with Attila the Hun,
Attila the Hun, Attila the Hun
Though a village, he'll pillage,
and kill everyone,
I still love Attila the Hun!

Don