And ...

... suddenly it struck me like a ten ton hammer (SON!!! (name that band and song for 10 bonus points)) ...

All good theme tunes of good TV shows are totally unwhistleable. If that is even a word.

Consider:

Doctor Who. Very difficult to get anywhere near the pitch or the sustain.
X-Files. Again, the pitch is a ...bitch.
House. It doesn't even have a confentional melody, for christ's sake ...
Star Trek:The Next generation. I keep confusing that one with the theme tune of Dallas ... so that is unwhistleable. And unmentionable.
Gilmore Girls. One does not whistle such a noble and distinguished tune. One screams it with joy and glee.

See my point?

Started colouring Big Blue. Hope to finish tomorrow!