Harbor inn key frantic!!!!

I think that you have mixed up your words a bit there. There is no key inside the Harbour Inn. I think that you are talking about getting the key so that you can get into the Harbor Inn. Anyway, you will not be able to get into the Harbor Inn normally because the only possible way for you to get your hands on the Membership pass is to go to a Nintendo Event. If you cannot find the time to go to a Nintendo Event, then go to a store like Wal-Mart and buy a little device called the Action Replay DS. This cheating device will give you a code that you can use to get the Membership pass(Harbor Inn key) automatically. You need to go in there to get Darkrai.

Hope this helps.

The only way to get the key is to go to a nintendo event and you mixed your words up there is no key inside harbour inn when you get the key you sleep inside the inn then you go to an island and Darkrai's there level 40.

Firstly the action replay that I got didnt come with the code for the members card, secondly to be allowed access you must have unlocked national dex and seen cresioli and healed the boy in canalava port city.
And the harbour in takes you to darkrai.
The code for members card is;

94000130 FCFF0000
B21C4D28 00000000
B0000004 00000000
0000AA3C EDB88320
2000AA68 0000000X
D2000000 00000000

Simply put 8 where the X is and then press L+R and go to any pokemart and there will be a guy in green
He will give it to you.
Also putting A in the X spot will give you the Azure flute in the same way, which allows you to catch Arceus!!! At spear pillar (top of mount coronet)
And a 9 instead of X will give you oaks letter. Which will let you go after the last of the trio shaymen or something, in a side patyh of Victory road.
Hope it helps