The last 3 years my kids have wanted to do brother/sister team costumes for Halloween. In 2011 they were Finn and Jake from Adventure Time. In 2012 they were Mordecai and Rigby from Regular Show. This year, they wanted to be Spy vs. Spy.
They don't read MAD magazine but they watch the animated sketch show on Cartoon Network and love the stop motion Spy Vs. Spy vignettes. This may be the last year they want to do a team costume so I had to oblige.
For the mask, I started with some stiff fusible interfacing - one layer in the shape of the mask and one smaller layer for stablity. Between the two layers I inserted a piece of sheer black satin and straight-stitched around the eyes, then trimmed the excess satin.