u can't get behind it as far as i know maybe u should get on at a certain time I've beat the game and still can't get back there if u find out put it on this site
go to the Pokemon mansion and go left and there is a door. go in the door and talk to the guy in the purple suit.hes the guy who owns the mansion.
Go to the Celadon Pokemon Center and go around behind it. Keep going through that little path and you will reach the backside of the pokemon mansion. You will notice a door, so you'll need to go through it to get into the pokemon mansion
The woman on the far right by the door? You can't move her. There is nothing behind her anyway.
NO!
Go to the Blacklot Mansion south of Hearthome, go into the hallway, go left hallway, then go inside the only door.
In the basement of the Pokemon mansion on cinnaber.
If you get the national dex, beat the elite 4, release your starter pokemon, go to prof oak or rowan (i can't remember), he'll battle you (beat him) and then go to the mansion. It's a surprise! Not really. Behind one door, there's LUGIA, and behind the next, HO-OH! Check it out. THIS DOES NOT WORK IN PEARL.
You go to the Pokemon mansion and the first door on the right go in talk to the two men then behind them there is a book and if you read that then you get manaphy added to the pokedex
A room full of money
The key is in the Pokemon mansion.
behind the door is leaf green u enter the Pokemon leaf green world
You can find the key to unlock the door in Pokemon mansion