He appears in the backgrounds of many of the strips of the main storyline (the mall, the movie theatre, etc.), usually in crowd scenes, and pictures of him appear frequently in Squee's room. He also appeared in I Feel Sick #1 in a crowded dance floor. Johnny seems to be in the habit of leaving his drawings lying around.
It is believed that Happy Noodle Boy's name is a reference to Johnny's extraordinarily thin figure. In one particular comic, Johnny says that when he was young, other kids taunted him for this, calling him "Noodle Boy."
At one point it is mentioned that, while all Johnny can draw currently is Happy Noodle Boy, he used to be an artist of particular talent.
According to Jhonen Vasquez, he created Happy Noodle Boy while attending Mount Pleasant. According to Vasquez, "So many years ago, [my little romantical friend in high school] was the unwitting reason Happy Noodle Boy was created. [She] always asked me for comics. But I couldn't draw as fast as she requested. Thus, I tried to create the worst abomination of a comic that I could, so as to make her not want comics anymore. That abomination, my friends, was Happy Noodle Boy".
4 strips of Happy Noodle Boy appear in Squee's Wonderful Big Giant Book Of Unspeakable Horrors.
The face of Happy Noodle Boy appears on the covers of JTHM in place of the Slave Labour Graphics logo.