The word "estimated" is misspelled as "etismated" during the "where are they now" captions at the end of the film.
During a scene in the second half of the miniseries, Mike Love's mustache starts to fall off when he's in bed and talking with his wife.
During a show which takes place sometime before 1963, the Wilson brothers' mom takes pictures of them, using a 110-format Instamatic camera. The 110 film format was invented a few years later than 1963.
When Mike Love gets into his Duece Coupe after talking to his father you can see the ignition switch is on the steering column. Since this scene was right after Brian gave Surf City to Jan & Dean that makes it 1963. The ignition switch was mounted on the dash until the very late 60s.
In the opening scene in 1960, a Wilson boy jumps out of the car with a skateboard. The skateboard has large composite wheels which weren't available to the public until the early-'70s.
Nik Vinet Was "Nick" when he signed The Beach Boys. However, his desk plate says Nik on the plate. He changed the spelling years later in honor of his grandfather.