The reason why i'm writing this is because I wroth it! Truth's. But please don't give me thums down. I accidently typed this cheat when I logged out. Whoops! <_>

Before you can get the Secret Key, you need the pokedex. But if you have 2 wonder cards you need to delete one of them. (Can someone tell me what a wonder card is in the comments please)

(You can get the Secret Key before you get Rotom if you want)
First, you need to catch Rotom. Use the hidden move Cut to get into the Old Chateau in Eterna Forest. Chech out the TV at nighttime, and Rotom will leap out at you!

The Secret Key is available via Nintendo Wi-Fi Connection from 8/6/09 - 19/7/09. In order to recive the Secret Key over Nintendo Wi-Fi Connection, you have to do a bit of preparation.

Step 1
Talk to the TV Producer on the third floor of Jubilife TV in Jubilife City.

Step 2
Answer his questions with these words:
Opinion on TV: Everyone Happy
Feedback on TV: Wi-Fi Connection
Then save the game and restart your DS/DSi system. (Hold down Start and Select and press L and R at the same time while holding Start and Select)

Step 3
If "MYSTERY GIFT" appears on the Start Menu, you've succeeded! Select "MYSTERY GIFT" to get started.

Step 4
Select "RECEIVE GIFT"

Step 5
After you select "RECEIVE GIFT", select "GET VIA NINTENDO WFC" and choose "YES."
Soon, a message will appear saying "UNLOCK THE SECRET!" Say "YES"

Step 6
Watch as you receive the Secret Key!

Step 7
Go to any Poke Mart and talk to the deliveryman dressed in green standing in front of the counter. He will give you the Secret Key.

Step 8
Now check your Key Items Pocket and you'll see that the Secret Key is there!

Step 9
The final step is to save your game. This is very important, so don't forget!

Once you've defeated Jupiter, take the Secret Key to the Team Galactic Eterna Building. When you enter, go left to hit the wall. Then go up next to the yellow and black thing. Press the A button while facing the wall next to the yellow and black thing and you'll unlock a room. Inside are 5 different electracl appliances - a microwave, a fan, a refrigerator, a washing machine and a lawnmower.
Choose one of the appliances with Rotom in your party and he'll change into the form you selected. Rotom will also learn a new move but you'll have to delete a previous move your Rotom already knows.

Good Luck!