Skeetendo

Anybody knows about the rumour about Mew under the truck in the Vermillion Port.
But almost nobody knows why there's a truck in there.

An Easter Egg?
Hmm, maybe, but I've found a more interesting motivation:

In Red\Blue there's an item, his value is 0x2D and it's a blank item slot, it's after the Secret Key and before the Bike Voucher.
This means this cut item was a Base Item, just like HMs or Itemfinder, that is important.

This item was a ticket.
A ticket for an island.
This ticket was an hidden item located in the Truck position.

Where the Ticket leads?
Hmm, ok, now there's one of the most interesting secrets of 1st generation.

Before the maps used for the Elite4 Lance there are 10 UNUSED Maps... why so much maps?
All these maps lead to Victory Road, suggesting that maybe there were some unused chambers in the Victory Road, but I discovered those maps - even if use the Victory Road as location - use different music.
One of those for example uses the Pkmn Tower Music.
That made me curious, so I investigated.

A Gamefreal developer admitted that he inserted Mew in the game just 1 month before the game release, during the Debug Stages, the last ones.
This was a big secret, only him and many other knew that.

They decided to put a sort of Event in which you may catch Mew, and this may seem correct (no?) and they decided to make it hard to reach: get in the Vermillion Port after the Surf Badge earned.
To do this you need to perform a small glitch: let at least 1 trainer that you don't have faced, get the HM01 and then lose against that trainer.
You'll be teleported back to Vermillion and the ship won't sail.

Then - with the plans those guys had in mind - you activated a special event by using that ticket somewhere (maybe at the SS Anne) that lead to the Island in which Mew is located... it wasn't displayed in the map since it had the same location of "SPECIAL" aka the Trading Room in every PC.

Those guys of Game Freak didn't did that because of:

1-Lack of time;
2- Too much risk to compromise the ROM... mess up the whole game in the Debug when everybody thinks the whole game is ok and then sell it may have been a huge disaster, so they removed the item and the hidden event that was placed instead somewhere else with another object (maybe the unreachable hidden Nugget in Safari Zone?).

That's it, an even t for Mew in an island was planned but then scrapped while the ticket was done and then cut.