Yiddish: A goat has a beard too, and it's still just a goat.

Appearance is not a reliable reflection of character.  SOURCE: Bernstein, Jüdische Sprichwörter und Redensarten.

אַ ציג האָט אויך אַ באָרד און איז פֿאָרט נאָר אַ ציג.

A tsig hot oykh a bord un iz fort nor a tsig.

A goat has a beard too, and it’s still just a goat.