What cartoon characters that are played by the same actor, but are so different, and you find it hard to believe it is the same guy or girl playing that part. You can better understand when I list some examples.
Ron Perlman - Slade (Teen Titans) and Mr. Lancer (Danny Phantom)
Grey DeLisle - Azula (Avatar: The Last Airbender) and her squeky sounding geek girl characters like Tootie (Fairly Odd Parents) Lizzie (Codename: Kid's Next Door)
If you want to go way back, any Mel Blanc character. His characters all sound like different people, and there is no tell that they are played by Mel. Mel Blanc is the Babe Ruth of voice over actors.
Ron Perlman - Slade (Teen Titans) and Mr. Lancer (Danny Phantom)
Grey DeLisle - Azula (Avatar: The Last Airbender) and her squeky sounding geek girl characters like Tootie (Fairly Odd Parents) Lizzie (Codename: Kid's Next Door)
If you want to go way back, any Mel Blanc character. His characters all sound like different people, and there is no tell that they are played by Mel. Mel Blanc is the Babe Ruth of voice over actors.