who composed it?
Stephen Hillenburg,
SpongeBob SquarePants (season 1)
The first season of the American animated television series "SpongeBob SquarePants", created by former marine biologist and animator Stephen Hillenburg, 
when did the first episode of spongebob come out May 1, 1999,
wiki:16259226
SpongeBob SquarePants (season 1) [SEP] Introduction
The first season of the American animated television series "SpongeBob SquarePants", created by former marine biologist and animator Stephen Hillenburg, aired on Nickelodeon from May 1, 1999, to March 3, 2001, and consists of 20 episodes (41 segments). The series chronicles the exploits and adventures of the title character and his various friends in the fictional underwater city of Bikini Bottom. The show features the voices of Tom Kenny, Bill Fagerbakke, Rodger Bumpass, Clancy Brown, Mr. Lawrence, Jill Talley, Carolyn Lawrence, Mary Jo Catlett, and Lori Alan. Among the first guest stars to appear on the show were Ernest Borgnine and Tim Conway voicing the superhero characters of Mermaid Man and Barnacle Boy, respectively.