He first appeared in the Bowser Junior's Summer Schoolseries as a sick, socially awkward, nerdy child, but he has since become a main character and has become more mature, logical, and an unashamed, raging homosexual.
He is the only character introduced in the Summer School series to appear outside of the series. He is mostly known for his weird, perverted personality, but is sometimes very smart.
He was born on February 29, 2008, which was a leap day, which only occurs every four years (ending in 4, 8, etc.) which are divisible by 4. In real time, he is 11 years old, but since his birthday has only occurred twice since his birth, he is often picked on by Junior and Joseph for being "two years old".
Cody likes to show off about how he is super hunky and how he takes pictures and paintings of himself, but clearly it is photoshopped.