In the scene where the Beatles attend a reception with reporters, John is asked if he has any hobbies.  He obligingly writes his answer down and gets this shocked response!  If you haven't been able to figure out what he wrote,  click on the picture to load a slow motion close-up video.  (You will need a movie viewer  such as QuickTime which handles .avi format.)  

Scroll down below the picture to read my conclusions.

  Watch his hand movement closely and I think you'll get it!

 First a definite horizontal line, then, somewhat harder to catch as flashbulbs create a distraction, two vertical lines.  Another definite horizontal , another vertical. Then a squiggly line.  Finally he backtracks to add something to an earlier letter.

That gives us  ___ |     |     ___ |     S     .

When properly arranged (dare I say "stacked"?), it spells out John's hobby!

___  .  ___            

|   |   |   S        

(If that doesn't come through correctly aligned on your browser, the answer is "tits".)