Joe made his first strip appearance on April 7, 1995. Joe is an expert marbles player and is portrayed as the neighborhood bully. He uses a cruel trick to cheat Rerun out of his marbles, but Charlie Brown eventually finds a way to win them back.
The strips in which Joe Agate appeared were adapted for the 2006 animated television special, He's a Bully, Charlie Brown. He appears as the main antagonist, robbing many innocent children (including Rerun) of their marbles. It is mentioned that he is the son of the trading post's owner. In the special, Joe actually beats Charlie Brown at first. But after realizing that Joe Cool (Snoopy) was holding on to two of his marbles, Charlie Brown is given another chance to play Joe Agate and manages to win back all the marbles for the children.
While not specifically identified as Joe Agate, a similar-looking bully makes an appearance in the 1990 animated television special, Why, Charlie Brown, Why?. The bully is shown mocking a young cancer patient, Janice, for wearing a hat and having a bald head. This leads Linus van Pelt to angrily confront him, The bully soon apologizes and is seen at the end of the special cheering when Janice reveals that her hair has grown back. Considering the special aired five years before Joe Agate's debut in the strip, however, it is unlikely to be him, though the design might have influenced the character's appearance
- Joe Agate is one of the many characters to appear on the app, Snoopy's Street Fair. For his booth, he challenges the visitors to a game of marbles, and tells them that when he plays, he plays for keeps.