Jaguasaur is a recurring monster, who's half jaguar and half dinosaur, in Mech-X4 who's created by Principal Grey both former and flying form. Jaguasaur was reused so Seth could rescue the MECH-X4 Team in The Arctic.
- Jaguasaur was terrorizing Bay City High in Let's Call It MECH-X4!.
- Jaguasaur was defeated by Mech-X4's Plasma Punch.
- In Let's Get Some Air!, the Mech-X4 team went looking for the monster heart to cure Harris.
- Jaguasaur's monster heart was dry and unable to cure Harris.
- Harris wanted to use Harper Futuristics Quanta-Burst Nano Laser in Let's Open The Monster Heart! to open Jaguasaur's Primorphous Core.
- Grey threatened Ryan that if Ryan doesn't give her the primorphous core, she would take Mark.
- More about Jaguasaur's history was shown in Let's Dig Deep!.
- Seth used the ooze, he first found in a cave, to create Jaguasaur.
- Since Grey had the primorphous core, she was able to upgrade Jaguasaur with wings as seen in Let's Be Idiots!.
- Grey ordered Jaguasaur to take Mech-X4, with Mark inside, to her location in Let's Survive in the Woods!.
- In Let's Get Our Robot Back!, Jaguasaur fought Mech-X4 and got defeated by the Grappling Grip and Plasma Punch.
- To help the Mech-X4 team get to Seth's headquarters, which was in The Arctic, Seth reused Jaguasaur in Versus The Wolves at the Door.
- In Versus The Thirty, Seth mentioned that Jaguasaur carried Mech-X4 back to Bay City.
- Jaguasaur was the first experiment with the ooze Seth found in a cave.
- Jaguasaur is the only monster to make several appearances in the show.