I don't know how Beatle-y this song really is but I thought for years that Paul McCartney sang the line "My belle ami, I'm in love with you" and the little harmony part. I know next to nothing about these guys but I know now it wasn't Paul! I think at least one of them is wearing Beatle boots though and I really like the Mustang the girl is driving.
I know the background harmony vocal you're referring to. Yes, it did sound like Paul. Very much so!
Stuck in the Middle with you - Stealers Wheel
ARRRRRGH; I just hit "preview" and the link/graphic turned up just fine, like everyone else's! I give up on trying to post photos and links on here. I guess I'm just a hopeless technophobe!