For Halloween 2008, our sons chose "Monsters, Inc." as their theme.
Our younger son (age 2-1/2) had a Mike Wazowski Costume. We live in Phoenix and didn't want his costume to be too heavy or cumbersome (in case the night was warm). Due to the amount of batting I used, it did end up being a little warm but adorable!
For the face/head, I used light green satin fabric. (Cost: About $7) I outlined a "Mike Wazowski shape," sewed it up on the sides, sewed the front and back together at the shoulders, and left the bottom open. For the horns, I hot-glued two pieces of gray felt together and hot-glued the horns directly to the fabric. (Doubling the felt helped them stay up straight.) (Cost for felt: About $1)
I found a light green long-sleeved shirt at a local thrift store. I bought a size larger than he normally wears so the sleeves would be too long. I cut triangles out at the tips to resemble fingers. I also found a pair of light green pants at the same thrift store and bought them bigger too so I could do the same treatment on them as I did the shirt (thus, making toes). I painted the tips of the fingers and toes using a black Sharpie pen to resemble fingernails and toenails, respectively.
I sewed the bottom of the satin fabric to the bottom of the long-sleeved shirt. That way, I could stuff the "face" all the way around him with batting, make it round, but he could still put his head and arms through the top.
I used white, green, blue and back felt for the eye. I simply hot-glued each piece together and hot-glued the entire eye to the satin. For the mouth, I used black felt with little white felt teeth, hot-glued it together and again, hot-glued it to the satin.
We bought a construction helmet and spray painted it blue. I hand-drew the logo on Avery label material and stuck it to the helmet.