You can't open the door. It has no use for completing Wimpy Wonderland
Apparently you don't need to go in there...
you give greg the video game guide then return the game to rowely and then he give you are credit card and open the laudry room and turn off the power.
You have to use the Joshie membership card you got from Rowley after getting into his house, to open the door to the left in Greg's house. From there, you will find an electricity panel and you can turn his electricity off. He will then leave the house and you can get in :P
You shut the front door
give the twisted wizard game back to rowly then use the card to open the laundry door then turn off rodricks power thaen go into the garge get the leaf blower and use it on freggly
you open the door to the laundry room with the joshie credit card and turn the power out in rodricks room then go in his room and get the dog bowl then talk to the man again measure 4 liters of wiper fluid
you have to get rowlys joshie membership card and that's how you open it ( !)
Use it to open the laundry room door at Gregs house.
You have to get the card from Rowley,Use it to open the laundrey room, and turn off Rodricks power. Then he will walk away and you can go out side. Rodrick drove his van away and you can go in.
you open the laundry room door with it in Greg's house.
to do so get the guys bingo troll and you can get in
it's a trick I completed the island and didn't need to open it