Does the Fokker 70/100 Flight Management Computer really contain the ability to play Pong?
The 'clip' is obviously a fake. Standards for avionics software development and testing are rigorous, with development of flight critical software being done by separate (independent) groups and legally required to be reviewed by another (independent) group.
After that testing is done by another group/person who's certified by the regulatory authority. It is very very difficult and downright dangerous to have this kind of codes in flight critical system software.
Also, as BowlOfRed says, there is a point in the video where the finger (of copilot?) goes behind the screen.

Also, from the clip, it appears that the two 'players' predict each other's moves pretty accurately. I'm not very sure if that's the way it is played, but I doubt it.
Of course, to prove that something is impossible is not possible, but I'm quite certain that the clip is a fake.