Shrek: [to Donkey] WHY are you following me?
Donkey: Oh, I'll tell you why.
[starts to sing]
Donkey: 'Cause I'm all alone / There's no one here beside me / My problems have all gone / There's no one to deride me! / But ya gotta have friends...
Shrek: STOP SINGING! Well, it's no wonder you don't have any friends!
Donkey: Wow! Only a TRUE friend would be that truly honest!