It doesn't fit the door at MacGuffin's. Try next door at Good Deals. You can use the toy robot to keep the lights on.
There is no key to MacGuffin's or its back room. The key that you do recover fits the back room at Good Deals next door.
Once you have the key that says "back room" you only have to go next door to Good Deals, and use the toy robot by the camera to keep the lights on.
Dont do it
It doesn't fit the back room at MacGuffin's so you should try next door at Good Deals electronics. Use the toy robot by the camera to keep the lights on.
There is no back room there. Someone answered another question incorrectly. The "back door" key fits the Employees Only room at Good Deals. You will need to use the toy robot next to the camera there to keep the lights on.
Not the back room of MacGuffin's, but the Employees Only room at Good Deals next door. Use the toy robot at the camera to keep the lights on.
You can exit the mall through the security room, and the blimp is to the left of the mall.
You do not get that key during the quest. The key that is eventually dropped in MacGuffin's fits the back room at Good Deals next door.
You don't have to, and you can't. Just a random blue arrow there.
After he knocks you down in the Carnival Costumes store, go to MacGuffin's and hide there. When he enters, you can surprise him. He gets away, but drops a key marked 'back room.'
Exit the mall through the security room, then go left to find the blimp.
You don't have to, and you can't. It is just a blue arrow item for no reason.