We knew for nearly an entire year that we wanted to dress our daughter up as an Oompa Loompa, as that's what we often referred to her (given her toddler proportions). The most difficult part of the Classic Oompa Loompa Costume was finding the right shirt and pants; so basically it was a piece of cake and I put the whole thing together the night before Halloween in a short amount of time.
First located these items of clothing: brown turtle neck, thick white pants and brown socks (from Baby Gap). I was prepared to make the pants to look more oompaloompish; however I ran out of time.
Other materials were: 4 big buttons, 2 strands of thick white ribbon, large safety pins, masking tape, hair rollers, orange and white face paint, green spray hair color.
I think I got the masking tape idea from someone else and it worked great for striping the collar, cuffs and socks. We tucked her pants inside her socks. I used the ribbons as the overalls, criss-crossing them in front and back, and safety pinning them to the back of the pants. The buttons were threaded to the outside.
We sprayed her hair green (all washed out no problem), rolled it up around the bottom with green rollers and pulled up a tuft on top with a pony tail holder.
Face was painted orange and we used white face paint crayons to paint over the eyebrows. We weren't sure how she would respond to painting her face; but she was totally into it and ended up applying most of the orange paint herself. The best part of the costume is that after Halloween, I pulled off the tape and buttons and she still has an outfit for the rest of the year!
In addition to the costume, I made her a Wonka bar with an image from the internet printed on glossy paper, cardboard and some gold wrapping paper that I had on hand. Her trick-or-treat bag was a canvas bag I labeled "sugar" with electrical tape.