This one is too easy.
April 20, XXXX was, and will continue to be, the day countless youths first got to know the effects of the sweet cheeba smoke. Surely, an individual walked into your friend's house or college dorm (if you lived a sheltered life) and began talking all sorts of logic to you about having a good time and how you needed to take a hit from his obscenely large glass bong. The cheesy glass art on the bong probably made you flinch at first, but after the first hit, you somehow began to find aesthetic merit in the wide-eyed frog and melting mushroom design, feeling as if "you got it" and had joined a new club. This appreciation was short-lived, as you were then pressured into taking another hit to impress the red-eyed, crusty-lipped guy next to you, who kept smiling even though he had a good deal of food in his mouth. Then, you and your cohort thought it was a good idea to make quesadillas and watch late night television in another room. However, in the midst your crazy-high, you forgot to take care of the bong and ended up causing a small fire. Someone's dad was not happy that from what I remember.
Anyways, Conan O'brien was especially good that night, and you surely thought his microphone was actually instead his penis, and he was sitting their interviewing someone with a huge erection in some fucked up universe where that wasn't a big deal. Due to the noise of laughing, you became paranoid and thought you got a visit from a weird authority figure, but he ended up being imaginary. He will later return during other experiences. At least that's what 4-20 has always meant to me.