Complex sentence: White's casting ultimately influenced Gaston's design; the animators adjusted the character's appearance after hearing White's operatic singing voice for the first time, making Gaston similarly operatic in his movements, gestures and mannerisms.
Split into simpler sentences: White's casting influenced Gaston's appearance; the animators adjusted the character's design after hearing White's operatic singing voice. They made Gaston similarly operatic in his movements, gestures and mannerisms.