I always thought this was a relatively interesting fact about Portal 2's strange development, so allow me to swoop in:
"Mel" actually comes from the Portal writers themselves, despite the low comic value - accounts vary, but Mel may have one time been the protagonist of Portal 2 (before it was changed back to Chell after negative reactions in playtesting). Numerous sources (here and "The Final Hours of Portal 2") also state that Portal 2's co-op originally featured "Chell and Mel" before they went with the robots... because not only are they so lovely, and expressive and *right*, but because we can accept them dying repeatedly and springing back to life
