When Marrissa Roberts left for the past, thinking she killed GLaDOS, it turned out that GLaDOS was not quite dead. She noticed Chell, whose butt was now missing, and suggested that Chell pick her up and insert her into her booty. Chell proceeded with this, and the result was CHELLGADOS, a humanoid robot for which Chell was the main body and GLaDOS, while in the butt, was the brain.
When returning to the future, Marrissa had first noticed CHELLGADOS. Then she brought out Atlas and P-Body, who Marrissa attempted to kill, only for CHELLGADOS to deploy them again. Marrissa also encountered Ratman, who was fighting against bad robots, but CHELLGADOS shot him into space via portals. Therefore, Marrissa went off to fight CHELLGADOS, but couldn't quite force herself to, since of CHELLGADOS's origins (Chell and Caroline, as GLaDOS).
However, upon this thought CHELLGADOS was reminded she used to be Caroline and that she has speshul powers. But before then, Atlas and P-Body appeared again and together with Marrissa opened a black hole so the GLaDOS parts of CHELLGADOS were sucked into space. This didn't end too well, though; GLaDOS had already damaged Chell too much and she died shortly thereafter.
- MarissaTheWriter commented on why she chose this name over "CHELLGLADOS": "I NO THAT GLADOS IS SPELLED GLADOS I CALLED HER FUSION CHELLGADOS BECOS CHELL ALREADY HAS THE LS AN IT SOUNDED MORE COOLER!"
- ITS MY LIFE! (First appearance)