It definitely wouldn't be the same show, if some of the characters were missing during the introduction of the series. I probably wouldn't care for it as much, though I MIGHT still like it. However, I probably wouldn't be as interested, if you took out any of the major characters. Remove Bloo or remove Mac, I probably would not continue to watch the show (to me, doing so would break up a really nice chemistry of two great characters). So, let's hope that never happens.
