On January 25 1968, The Beatles dropped in to Twickenham Film Studios in London for the task of appearing in a cameo for the upcoming "Yellow Submarine" feature film based on the song. In the end, the cameo lasts less than a minute. The Beatles are seen in similar shirts and the background is black. The original idea was to have animation happening in the background during the cameo, but this failed to materialize due to budget constraints and time constraints. It's a nice little ending and it's great to see the group together for this segment as they introduce the last song "All Together Now" which would end up on the songtrack, of course.
Also taped on this day are segments of the individual Beatles hanging out in the animation studio with Paul listening to a playback wearing headphones, Ringo looking through one of the movie cameras and George running across the studio holding a tape measure. These brief scenes appeared in a short documentary on the film entitled "A Mod Odyssey" which is available commercially on the "Yellow Submarine" DVD (1999 version as well as the upgraded 2012 version).