Simplify the following text for a Grade 9 native English-speaking person.
Original: This episode marks the first full-fledged appearance of Kent Brockman , and Kelsey Grammer makes his first guest appearance on the show as the voice of Sideshow Bob .
Simplified: This episode is the first full appearance of Kent Brockman , and Kelsey Grammer makes his first guest appearance on the show as the voice of `` Sideshow Bob . ''