It took my wife to point out John Cleese (and I thought I was such a Python fan)
In your defense, Python-era John Cleese did all sorts of funny voices; pretty much everything I've seen or heard him do in more modern times, though, has had him speaking with what I think of as that distinctive John Cleese sound (though whether that's by personal choice, instruction from directors, or a loss of vocal dexterity with age, I don't know). So now that you have a vocal reference point for him in
Shrek 2, I'd say you'd only have to be embarrassed if you don't recognize his voice
from now on.