Grenade Guy is a humanoid grenade monster
At the Halloween party held at Zoom Comics, Frankenbeans (who had left Hillhurst) tried to blend into the costumed crowd. Soon, Grenade Guy was there to kidnap him while the Beetleborgs were distracted. In the ensuing battle, Grenade Guy overpowered Roland, but then the Beetleborgs decided to try a new maneuver with their AVs. Jo equipped her AV with the Blue AV's magnet attachment to capture Grenade Guy, who was being held still by Roland's Hunter Claw. She then dropped him onto the other two AVs which were waiting to finish him off.
Grenade Guy reappeared during the "Curse of the Shadow Borg" saga when he was brought out by Vexor.
Drew says he is from issue #101 from the comic book series.
Grenade Guy also had a powerful counterpart in Super Grenade Guy.