Simplify the following text for a Grade 9 native English-speaking person.
Original: `` Bart the Genius '' is the second episode of The Simpsons first season , which originally aired on the Fox network on January 14 , 1990 .
Simplified: `` Bart the Genius '' is the second episode of The Simpsons ' first season , which first started on the Fox network on January 14 , 1990 .