@AukeXI: Riddler Room: You need the mirror and the puzzle. This will be the second to last room, so yeah. XD Anyways, use the mirror on the puzzle and the name will show. The option doesn't even appear until you do that. XD Simplest yet the second most difficult room at the same time.
(Sorry for taking up so much space. XD I just think this might help people.)
Sideshow Bob: Get the paint and the paintbrush and drag the paintbrush onto the paint. Eat the banana (OMG! SHE'S GONNA EAT SOMETHING! :O) and paint the peel. Walk into his room and drop the peel on the floor. Get the knife. This knife helps you complete the Mask's room.
Leatherface: Okay, kinda difficult since you need to be FAST. First, open the umbrella from the Penguin's room. Go into Leatherface's room (room next to kitchen) and jump out the window. Grab the umbrella and drop it on Lady Gaga. She'll float down and go up the stairs when she lands. Grab the dog with the mask on and drop in onto Leatherface's body. :D Easy, right? Get the mirror and if you want, the (useless) chainsaw.
Mask's Room: First of all, get all of the items from the kitchen and flatten the dough. Put the tomato sauce on the flat dough and go finish Sideshow Bob's room. Anyways, cut up the ham and cheese and put it on the pizza. Put it on the shovel, open the oven and put it in. When it's done, go get the sleeping pills (unless you're like me and grab everything as you go) and put the on the pizza. Put it in the box and be quick to give it to the Mask dude. Collect the dog and mask and put the mask on the dog. :D
The Penguin's Room: Funniest room in my opinion. First of all you must finish the Grinch's room and get the boots from his room, along with the Martian's room and get the water gun. Put water from the hot water thermos in the kitchen into the water gun and put the boots on and walk into The Penguin's room. You'll have five seconds to melt the ice below him. Get his umbrella. :D
Fat Tony's Room: Get the cigar from the room outside of his (stack two boxes on top of each other and climb up and get the cigar) and put it in the vent. The enter his room, get the paintbrush from behind the char and the baseball bat. On your way out, get the paint.
Okay. This is a walkthrough if you need help. :D Room by room (no particular order...I just put them in any order I wanted to okay!?)
First of all, we need to establish that the kitchen is the door leading up from the first room. Okay. Go To the Joker Room (I'm not gonna map out directions! Sorry!)
Joker Room: After the 'chatting' between Lady Gaga and the Joker, go pick up the flashlight, puzzle board, and puzzle pieces. Combine the board and pieces and do the puzzle. Turn off the light and carry the flashlight to the puzzle. Memorize the four digit number and quickly put it into the keypad next to the 'exit' door. Yay! You can continue to help the blond pop singer!
~continued in next comment since this game is pretty long (sorry)~
 "Lady Gaga Saw Game")
 "Monsters Fight")
 "Ayumilove HackerStory V1")
 "GeoSketch")
 "Billys Big Adventure")