This year, the Professor's sister, Aunt B, decided that Miss S ought to be Mario for Halloween. I waited until everything else was mostly done (while the kids were at school on Halloween, actually) and then did what I could. Here is what we were going for, more or less.
Next came the hat. Aunt B had sent me directions (here) and given me fabric scraps she had. I mostly followed the directions (shrunk slightly to fit the fabric and because Miss S is a baby), except for the M. I used the computer to trace the M the size I wanted it on a paper pattern. I used craft glue to glue the M and the circle to the hat. (Another time, I would glue the M and sew the circle.)
To finish up, I used the Professor's great idea. I cut a mustache out of black craft foam and stuck it on a pacifier with blue sticky tack. To get the shape, I used the top of the pacifier as a guide and then curved the bottom to make it more Mario-like. I also left a space in the bottom so it fit around the pacifier well. I liked the total effect, even if Miss S periodically took off her mustache.
(And here we have Miss S and Aunt B (in her fabulous Lucca costume.))