I dint usta be abel to spel muleclar biologist, but now I are one...Even though us molecular types don't usually study anything closer to sex than DNA, we sometimes can recognize that there's SOME sort of interesting activity being discussed in some of these songs.
I think Bob Landry said Bert's song WAS the one he wanted; in my somewhat twisted frame of reference, even THAT on sounds a bit risque:

"He'll sing to every boy and girlie his little serenade on wood...

Come on and try his rhythm and let your heart beat with him..." Just what is he doing with those kiddies?

As Professor Lehrer once said,
"In the appropriate mood, EVERYTHING'S lewd;
I could tell you stories about Peter Pan,
and the Wizard of Oz, there's a dirty old man!"