Chell as a Regressor with GLaDOS as a Caregiver from Portal
Since Chell already doesn’t speak, it’s rather difficult to tell at first glance when she regresses. However, GLaDOS is familiar enough with her testing methods to notice the difference. She gets distracted more easily, and once had a very close call when she apparently tried to play peek-a-boo with a turret.
Ever since, GLaDOS has kept a careful eye on Chell’s testing speed and focus, and whenever there is a significant dip below average, she will make a point to either replace any turrets in upcoming tests with defective ones or remove them entirely. Acid pits will also have to go, just in case.
The aerial faith plates stay, though! In fact, they are added in excess. Chell loves flying through the air and bouncing on them like a trampoline.
Once GLaDOS set up a testing chamber that was just one really long chain of faith plates going back and forth across the room and it honestly was hours and hours before she could convince Chell to move on to the next one.
GLaDOS had to install a wireless override/child lock for the portal gun to turn it off herself because little Chell will make those infinity fall tunnels and then get stuck and make herself sick.
Every cube becomes a companion cube to Chell when she’s little. She’ll go to them or spawn them right from the beginning of the chamber and then carry them around the room as she solves the test, then pitches a fit when she can’t take them with her to the elevator.
GLaDOS is still adamant about the testing rules even when Chell is little, so these tantrums over the cubes get very tedious. It’s partially a safety issue, and partially that GLaDOS doesn’t want to set a precedent that Chell can get whatever she wants just because she’s little.
Whenever Chell throws a particularly bad tantrum over the cubes, GLaDOS makes sure that the next test doesn’t have any cubes at all. If Chell can’t be safe and follow the rules, then she doesn’t get to play with the cubes, simple as that.
However, whenever she is good about leaving them behind, the next chamber always has more cubes and even the special mirror cubes with (alternative, non-lethal) lasers to play with as a special treat.
Chell notices this pattern over time and starts “putting the cubes to bed” at the end of each test, tucking them safely right next to the door and pretending to tuck them in for nuh-night. It helps her cope with having to leave them behind.
After a while of good behavior with the cubes, GLaDOS surprises Chell with an extra-special treat in the next chamber: all the cubes ARE companion cubes now, complete with the little heart design! Chell gets so excited over it and ends up playing with them in the chamber for hours, stacking them up and climbing on them and everything in between.
When she finally does finish the test properly and gets ready to leave, she almost throws another tantrum when GLaDOS reminds her that she can’t take the cubes with her. She’s huffy over it for a minute, but eventually tucks all her cube friends in the corner to put them to bed like she learned to do.
She’s happy to discover that every cube in every chamber she’s little in after that continues to have the companion cube design.