You get the key for Good Deals when you surprise the robber at MacGuffin's. (He knocks you down at the Costume store.)
There are no coins used on Night watch island.
you use a toy bird found in the toy store.
Crawl Mart is in the left (west) wing of the mall, next to Jolly Gifts toy store.
What you got it for: cut the padlock on the empty store (first floor next to Sizzle).
Not sure why you would, as this is not part of the island quest. You only go into the joke store (Jolly Gifts) as part of the Bonus Quest.
night watch island
It is in the right (east) wing, on the third floor to the right of MacGuffin's and Good Deals.
The lights will stay on whenever there is motion by the camera. Use the toy robot from Giuseppe's and it will walk around there.
You can use it in the Good Deals store, where the lights only stay on when something is moving in the front by the camera.
The "Back Door" key fits the employees-only door at Good Deals Electronics. (use the toy robot by the camera to keep the lights on)
Back Lot Island (April 2013)
The robot birds are in Giuseppe's Toys when you respond to the alarm and find the Toy Robot is the cause.