1:35--Mark E. Jerry?

Also, what the fuck is "do lay-by"?

Different lyrics, different instruments, faster tempo, but same melody, I'm tellin' ya.

Shaggy did a cover of this stinker. I think it was the b-side on the "Mr. Boombastic" single.

Every time I've heard that Devendra Banhart guy I have instantly thought of this song. His vocal delivery seems to be entirely based on it.

Also, the Gershwin melody is not particularly close to the Mungo Jerry one, aside from starting high and descending during the phrase. Play them both, it's a totally different pattern. I'd struggle to consider 'In The Summertime' to be anything more than very loosely inspired by 'Summertime'.