Whitney is shown in Marine dress blues as a Private First Class (E-2) with the "blood stripes" on his trousers which is only worn by NCOs and Officers (E-4/O-1 and up). Since this is actually Tina pretending to be Whitney this is a character mistake.
In the scene where Clark plays pool with Lex, there is a point where they stop play to talk. At that point Clark picks up the #10 (blue striped) ball. Clark later rolls the ball across the table, when the camera cuts away the ball that's rolling is now the cue ball and not the #10. Other balls on the table change positions between the shots too.