Triplesaurus Rex is a blue 3-Headed Tyrannosaurus monster with two short arms and two long tail-shaped tentacles
In "The Old Gray Flabber," Les had drawn a portrait of Flabber which caused him to get old (in a situation akin to a revered "Picture of Dorian Gray"). Les then drew Triplesaurus Rex to distract the Beetleborgs from Flabber's rapid aging. After Triplesaurus Rex was seemingly destroyed by the Beetleborgs, his 3 heads came back to attack them. They ended up getting taken out of the picture also.
In "Mega Borg Power," Triplesaurus Rex's picture was seen among the many of Les' drawings that were combined with toxic chemicals and Nukus' powers to create Repgillian.
- The costume for Triplesaurus Rex later appeared in Power Rangers in Space episode "Flashes of Darkonda" as a patron of the Onyx Tavern and later in the episode "Countdown to Destruction" as a member of the Machine Empire's army.