When Violet goes to set the cupcake down outside her door, you can see icing on the rim of the plate. However, when the camera jumps, the plate is clean.
(At 09:34 When Leah Moves Her Hat To Show Violet Her Hair Turning White). Hair Does NOT Change White/Grey Overnight, Only New Growth Will Be That Color.
The beginning opens to the 5th Dimension singing "The Age of Aquarius" with the date 1968 on the screen. But that album and single was not released by the 5th Dimension until 1969. Before then, theater cast members sang it for the "Hair" musicals onstage.
In the clips of Rowan And Martin's Laugh-In, Tennessee Ernie Ford was shown talking to Goldie Hawn in a skit but he did not appear on the show until November 1969. It would have been impossible to have this playing on TV a year before it aired.