Reefer Madness Movie; Subliminal Message

In the scene where Bill first enters Jack's apartment, there is some banter, and chitchat. Hit slow-mo, and wait. After that goofy redhead is done talking, the screen is suddenly put pitch black with the number "4" made out of green letters. Another split second later, the same black screen, except the number "20" appears.
It is impossible to see this without slow-motion, as it only takes a microsecond for both of these screens to pass.
This is really funny, as the film was a propaganda made in 1939 to prevent the "scourge of the evil weed" from spreading". Obviously this touch was added much later when they re-released the movie in color.
pce:stoned:

I think with the later releases, everyone knew that Reefer Madness was not to be taken seriously, so I think they just tossed that in there for kicks.

I'll have to look back on my DVD though. That's pretty cool. How did you ever discover that anyways? Just curious. :)