Originally Posted by Terraferminator
10 Tunnel Mouse
Played through every D.E.C
There are five versions of the D.E.C, four of which you'll go through as part of the storyline. Once you've got into the entrance of the D.E.C in Mean Street North you'll go through the first one.
Number 2 comes after OsTown, 3 comes after Rainbow Falls, 4 after Rainbow Caverns. To access number 5, you need to take the 'thinner' path through Fort Wasteland which involves thinning all the enemies instead of befriending them. If you've passed this level and befriended the enemies you may not be able to access this DEC. Make sure to get it on your 2nd playthrough if not.
It's posible to get both film buff and tunnel mouse with the same playthrough. After unlocking the projector in rainbow falls you can go back to devil falls and go back through the DEC, allowing you to get both.