i have no link but will also back up koshea, some kids would meet everyday after school for their usual routine and maybe one of them just happend to look up at the time one day and figure out that they always plan to meet at 4:20.
alternative ending: while blazing the best chronic cali has to offer the ganja fairie appears before the routinely smoking stoners, she goes on to proclaim them official potheads and deems them worthy of smoking her pot, she then goes on to give them mad props for finding the dro that is so stickylicious and proclaims 4:20 the official pot smoking memorandum(or holiday or something) the end

yes i like the second story myself
peace
thebubbler