Simplify the following text for a Grade 6 native English-speaking person.
Original: He did his most significant work for the Warner Bros. and Metro-Goldwyn-Mayer studios , creating the characters of Daffy Duck , Bugs Bunny , Droopy , Screwy Squirrel , and developing Porky Pig and Chilly Willy ( this last one for the Walter Lantz Studio ) into the personas for which they are remembered .
Simplified: He did his most major work for the Warner Bros. and Metro-Goldwyn-Mayer studios . He created the characters of Daffy Duck , Bugs Bunny , and Droopy .