Complex sentence: During the season's run, "SpongeBob SquarePants" became Nickelodeon's 2 children's program, after "Rugrats", upon which nearly 40 percent of its audience of 2.2 million were aged 18 to 34.
Split into simpler sentences: During the season's run, "SpongeBob SquarePants" became Nickelodeon's 2 children's program, behind "Rugrats". Nearly 40 percent of "SpongeBob" s audience of 2.2 million were aged 18 to 34.