http://wogew.blogspot.com/via WogBlog:
"In 1967, Wangberg finds himself in Sound Recorders Studio in Hollywood, one of many studios Brian Wilson decided to utilize for the recording and mixing of The Beach Boys' upcoming album, "Smile". Having already recorded the song "Vegetables" with Wangberg first as second engineer and later on in control of the engineering, the Beach Boys, Van Dyke Parks and Wangberg are there to put the songs together to make a coherent album when John Lennon and Paul McCartney stop by, together with Derek Taylor. After having congratulated John and Paul with the success of their latest single, "Penny Lane" and "Strawberry Fields Forever", Wangberg plays back "Vegetables" for the guests from England. After having harvested compliments for the song, Wangberg, still not sure about who is who of John and Paul, witnesses an encounter where Paul and Brian are both sitting at the piano, playing each other's new songs. "Sgt. Pepper" is still not released, so Paul starts by playing and performing "Fixing A Hole". Brian counters by playing and singing "Heroes and villains", and Paul answers with "Lovely Rita". Wangberg can still rewind Paul's solo version in his mind, he writes. Brian performs "Surf's up", before the party breaks up, John and Paul leave and "Smile" is shelved indefinitely...
This visit by John and Paul is not documented in Beatles history. In April 1967, Paul spent a week in USA with his assistant, Mal Evans - not John. During his time in LA, Paul did visit Brian and The Beach Boys in their recording studio (April 10, 1967, without Mal), and the story goes that Paul partly co-produced "Vegetables" with Brian, chewing a bit of celery during the proceedings, and also played "She's Leaving Home" to Brian on the studio piano. It's tricky to work John Lennon into the story here, but Paul gives credence to the tale in his introduction to the book. I believe more research should ensue."