If you don't have a proper gaming seat, then you could always make one that looks like a giant 555 timer chip or the infamous giant Fn computer key. But for something cute and Super Mario Brothers themed, here is a giant 1UP shroom.
Collect a bunch of boxes and make one yourself.
Step 1: Game Gear...
Lots of cardboard.
Refer to the other cardboard projects spammed in the introduction for tips on how to work with cardboard.
Having a giant appliance cardboard shipping box is nice but you can piece together smaller scraps salvaged from little boxes.
Cull those that are not coated or glossy with print, remove all staples, labels and tape.
Pick the sturdy boxes.
Paper for papier mache.
You can harvest the outer layers of cardboard to use as papier mache material but that is a lot of work.
I just have a ream of 65lb paper cover stock to use. Typing paper and newspapers will work but you will need a few more layers to build up the thickness whereas the cardstock covers nicely.
Lots of glue.
You will probably burn through a quart or more of glue. That is why I buy it by the gallon.
Carpenter's glue is good for it's tackiness and quick grab. Regular white glue is more economical and better to use for the papier mache part.
I had some leftover carpet padding from well, laying down carpet in the house, that could be another ible.
You can use upholstery foam, batting, fiberfill or most anything cushiony soft.
Seat cover material.
I found this green polka dot print at the fabric remnant store and purchased one yard.
It's not the giant polka dot pattern from the video game but it works. You can get a plain green fabric and paint or sew big white dots on it if you can't find anything similar.
Hot glue gun and some hot glue sticks.
Regular stapler with staples
Paint and primer to paint the base.
CAUTION: paper cuts, hot glue burns, all par for the course when working with cardboard. Be careful, it's a jungle out there!
Step 2: Barrel of Fun...
It is essentially a cardboard barrel. I guess you could substitute an empty 5-gallon bucket and go on to the next step but there is no fun in that.
Start out with a circle 12 inches in diameter.
Remember, things don't have to be too too exact. You can beat cardboard into submission and work around it.
Cut out about three or four more cardboard circles to laminate together.
This is the bottom of the barrel. You can piece together several smaller pieces of cardboard within each layer. Just overlap the seam with the next piece of cardboard. Try to alternate or change the direction of the grain or internal corrugation to give the piece more strength.
Get the feel for the cardboard if it needs another layer for reinforcement. It should not flex and will become more rigid as the glue dries.
Laminate each layer with plenty of glue, use clamps or weigh it down as necessary.
When the bottom disk is dry, form the barrel by layering up a wall about 15 inches high. The finished height will be about the same as a regular chair height to be comfortable.
Piece together layers if needed. Cut tabs on each layer to help transition the joint and to attach the wall piece to the bottom.
Step 3: Paper It...
A uniform skin over everything gives the structure some strength and makes it look good.
Tear off pieces of cardstock or whatever you are using as papier mache material.
Dip in glue/water or just apply glue and paste in position.
I added a detail piece for the eyes and papier mached over.
Step 4: Top Hat...
Form the sides that will go down about 2/3rds of the way.
Layer and laminate 3 or 4 layers of cardboard until it is rigid.
The mushroom cap is tilted on the character exposing the eyes. We will just make the bottom edge of the cap fit around the eyes by altering the length of the seat skirt wall.
Layer and laminate the seat portion to be able to have a person sit on it without deforming it..
Papier mache the cap.
Note that the cap turns out like a Spaceballs sized Darth Vader helmet. Hmmm, mebbe make one for Halloween. I think you can hear the ocean or an echo when you wear it. Anybody for a giant Legos Minifig?
Step 5: The Prime Directive.
Otherwise the bare cardboard will soak up a lot of paint.
You only need to paint the stem since the cap will be covered in material.
You can prime everything to seal all the surfaces.
Paint the stem in an off-white color.
Paint and detail the eyes in black paint.
Step 6: Cushy for Your Tushy...
Cut up pieces and tack in place with hot glue.
I did happen to burn a spot in the palm of my hand when pressing down on a piece and did not see the hot glue blob that was camouflaged by the random pattern in the carpet padding. The foam padding insulates so it takes longer for the hot glue to cool down and adhere.
When done, it should resemble something like a fluffy Kingon Bird of Prey.
Step 7: Cover Your Bottom...
You can hot glue if you have something to press against the fabric and hot glue since it will ooze through the fabric and burn you.
I think I would have tailored the cover a bit better. It looks more like a showercap with the gathered edge. You can take newspaper to mock up and create a pattern for the cap and then cut out your fabric to sew a better fitting cover.
I think I will get some proper batting to pad the seat and redo the covering.
But here you go, the 1UP Mushroom Cardboard Storage Stool.
Sit on it.