Charleyyy is the main character and the host in Bowser's favorite TV show, Charleyyy and Friends. He was the oldest of the summer school class (Episodes 1-2).
Charleyyy was a student in the Bowser Junior's Summer School series and attends the same school as Bowser Junior. The reason why he was taking summer school is unexplained. Apparently thought, part of Charleyyy and Friends was filmed live while Charleyyy was partaking in the class. Charleyyy only appeared in episode one of the series: he was marked absent for the rest of the series at the beginning of each class. By the end of the series, Jackie Chu, the teacher of summer school, declared that Charleyyy officially flunked out of class due to missing all of his classes (Charleyyy of course wasn't ever there to accept his failure, like the other failing students did). The reasons why Charleyyy kept not showing up for his classes might be because he was busy filming Charleyyy and Friends.
Charleyyy has received critical acclaim by the SML community, with many fans regarding him as one of the greatest characters in all of SML history. Fans have praised Charleyyy for his, somehow, entertaining stupidity, clumsiness, and constant upbeat attitude, regardless of many of his life's circumstances. Since the character's introduction, he has remained one of SML's most iconic and most memorable characters. He has appeared in several Charleyyy and Friends "episodes" (including various episode specials), a video game, and even a movie.
Charleyyy becomes friends with Luigi in Luigi's Mansion Episode 8 and it's currently unknown whether or not the two are still friends with each other.
In the alternate dimension, Charleyyy is replaced by Harleyyy.
The Charleyyy and Friends show is supposed to be targeted by young kids but strangely, Bowser enjoys the show and his video game is rated M for "Mature".
It is not known how Bowser started to like Charleyyy and Friends as it was first shown in Bowser's Biggest Fear.