Complex sentence: Scorpio is widely considered to be Albert Brooks'best voice performance on the Simpsons, and Brooks (who according to DVD commentary, ad-libbed the majority of his lines) was even named the greatest guest star in the show's history by IGN.
Split into simpler sentences: Scorpio is widely considered to be Albert Brooks'best voice performance on The Simpsons. He was named the greatest guest star in the show's history by IGN.