This is a really easy way to get Marvin from the Hitchhiker's Guide to the Galaxy up on your tree. Still trying to figure out how to get a lovely voice clip of Alan Rickman to go along with it, but we can't have everything.
The material list is fairly small:
Christmas bauble (go for frosty white or silver)
Black permanent marker
Using an elastic band to act as the black eye line guide, draw a line across the bauble with permanent marker. It's a bit tricky to keep a steady hand, but I found that the elastic helped a ton. Make sure the marker dries completely before you remove the band. The top part of the line, where it rested against the elastic, will have a bit of a rough edge, so try to carefully cover it with the marker again.
Snip off two corners of the lime green paper, so you have the triangle eye pieces. Using white glue, carefully glue them on, just below the black line you've drawn on the bauble. Make sure the glue dries completely, and try to get the eyes evenly spaced.
Once the glue is dry, take your marker and slowly outline the bottom edges of the eyes. If you used too much glue and some of it bubbled out, your line will be a bit rough, but shouldn't be too noticeable.
And that's it! A very simple Marvin the Paranoid Android ornament.