Complex sentence: In 2006, IGN ranked "SpongeBob SquarePants" 15th on its list, "Top 25 Animated Series of All Time", and in 2013, it ranked the series 12th on its list, "The Top 25 Animated Series for Adults".
Split into simpler sentences: In 2006, IGN ranked the series at the same spot on its list of "Top 25 Animated Series of All Time". In a 2013 list, the website ranked "SpongeBob SquarePants" 12th in "The Top 25 Animated Series for Adults".