In order to see the man on the roof, you must have a pokemon that can surf, not have the Secret Key in your inventory and be able to reach Cinnabar Island from the East(Right) side. Surf out into the water where you can't see Blaine's gym. Start to Surf back to land in the area that you can just walk to the door without moving North (Up) or South(Down). Walk onto land and go towards the door. It will say "This door is locked" Look on the roof. A useless, yet weird trick.
In order to fish in a statue, just go into any gym and go to the side of the statue that says "(City) Gym; Winning trainers: (your rival), (you) and take out your fishing rod. You probably won't find anything but it looks weird.
To stand on top of one of those trees you can cut down with "Cut", hack one away and stand where it was. Save the game and turn off your gameboy. Restart it and you will be on top of the tree. Yet another useless but weird trick.