The Beach Boys - "Barbara Ann"

"Barbara Ann" was not written by The Beach Boys.
The song wasn't even intended to be a recorded release in the first place.
Indeed, the Beach Boys had a contract obligation to release one more album within a certain time frame. Brian Wilson had already started producing "Pet Sounds" but had to put that aside for a while to meet this obligation. However, he didn't want to spend one minute on this more than necessary, hence the "Party" album idea : the Beach Boys simply decided to through a party at the studio (Mike Love went across the street to pick up some beer) and then simply recorded whatever they felt like singing. Jan and Dead (a then quite famous group) happened to stop by and got invited to join the party. They had previously recorded "Barbara Ann" and Dean suggested they sing that they sing it together, which they did. You can hear them partying in the background, one guy yells, "Pass me an ashtry" and you can hear a girl hollering, "Come on". The guy who was singing lead was actually Dean and not one of the Beach Boys.
On the uncut version, the Beach Boys keep repeating the chorus over and over, getting sillier and sillier (maybe the beer had started kicking in), and one can also hear a "Thanks Dean" shout, thanking him for suggesting they sing the song.
Available on the album "Beach Boys Party"