To pass the time...
I usually wait until the senior guy is in the bunk then try to close it with him in it.
Let's see what else...make waypoints in the FMS that show up while I'm in the back on break.
Waypoints like: Let the F/O have the chicken.
Next time you take the first break
Light a match, next time you use the lav
Other activities we play are: Don you lifevest inside the plane and try to jump rope, moon other aircraft when they fly by, and finally "let's see if the landing gear really work at 40,000 feet".
Never a dull moment,
FF