I'd seen images of Mario and Zelda coaster sets and had to sit down to make some. At the bottom of the post I included a few of the patterns that I created when making the coasters.
The perler beads are usually purchased at JoAnn fabrics with 50% or 60% coupons. The beads are cheaper at Michael's, but Michael's doesn't allow more than one coupon a day and the Michael's that I haunt doesn't have very many colors. Thankfully JoAnn's has tons of perler bead colors.
For the corkboard that I attach to the bottom of the coasters I went to Hobby Lobby and purchased a roll adhesive cork. I purchased the roll that is a foot wide as I can get three backings for each four inch cut.
The finished size of the coasters is roughly 4x4 inches and is a 20x20 perler bead square.