The squares I used were 5" each, with the I Love This Yarn yarn. This measures 70" x 90", to fit a twin-sized bed.
Most patterns shown only have the grid of Mario but don't say how they did the rest. Maybe you don't care how it's done or you'd rather do it your way, but I'll tell you how I did it my way, especially for those of you that aren't familiar (like I was not, when I began this project). I used a G hook for the squares.
The squares are as follows:
Chain 5, sl st into first chain. 3DC in each stitch around (15 stitches). chain 3 (the chain 3 will then count as 1 DC as you end each round).
R1: DC in 1. 2DC and 1TC in next. 1TC and 2DC. *1DC in next 2 stitches. 2DC and 1TC, then 1TC and 2DC in next.* Rep in * twice. 1DC. Sl st in to the 3rd loop of the chain you started with. This should bring it into a square where there are 4 DC followed by the corners on each side. (32 stitches)
R2: Chain 3. DC in 3. 2DC and 1TC in next. 1TC and 2DC. *1DC in next 3 stitches. 2DC and 1TC, then 1TC and 2DC in next.* Rep in * twice. DC in 2. Sl st to the 3rd loop of the chain again. You should have 6 DC followed by the corners on each side. (47 stitches, 48 when you count the chain.)
R3: Chain 3. DC in 5. 2DC and 1TC in next. 1TC and 2DC. *1DC in next 5 stitches. 2DC and 1TC, then 1TC and 2DC in next.* Rep in * twice. DC in 4. Sl st in to the 3rd loop of chain. You should have 10 DC followed by corners on each side. (63 stitches, 64 with chain.)
R4: Sc in each stitch around. I did 2sc in two stitches at the corners. Make sure you are consistent, whatever you do. (72 stitches.) This gives it the extra width to make the 5" square.
Measure your square to make sure your gauge is ok, if you are looking to do a twin-sized comforter like this. Each square should be 5", as mentioned before.
To piece each one together, I sc along the seams using an F hook. I turned the squares over on their back side to do so. I worked from top to bottom first, then put the seams together in those sections that were loose. I was pretty picky putting mine together: I had the squares all facing a certain way, etc. I actually accidentally put an extra stitch in each square, as I was teaching myself how to do granny squares, so your project may look a little "neater" than mine. By the time I noticed my mistake I was already about 30 squares in and I DID NOT want to redo them!!!! You can't really tell unless you look close anyway, but still--that was one reason I had my squares all facing one way.
For the border, I used a J hook and just sc around, putting 2sc in the corners much like I did the individual squares.
Here is the pic of the pattern I found on Ravelry.com that had the Mario I used:
As far as materials. I spent about $85 on yarn alone, and that was mostly without sales tax and sometimes with discounts!! So keep that in mind!! I could eke out about 14 squares per roll. This pattern takes 252 squares!
Green: ~2 rolls
Brown: ~3 rolls
White: ~4 rolls
Yellow: 1 roll
Tan: ~3 rolls
Blue: ~8 rolls
Total: 21 rolls. PHEW!
It took a lot of work and was pretty monotonous/tedious. The other part that most people don't mention is HIDING ALL THE TAILS!!! There are some 5 or 600 tails I need to "tuck in" still, and let me tell you, after all that I don't want to do anything else with it! Ha!