Woah, that's a nice comment :) It just depends on what is described. You look how? Perfect. An adverb, as it describes how you look. The duck seems to be... perfect. Adjective, as it describes the duck.
"Wydaje się być dobrze" (It seems to be good, with a very general 'it') takes an adverb, but it's rather connected to 'być' than 'wydaje się')