Chell
Chell is the player character in Portal and Portal 2.
Portal
In Portal, Chell is dressed in an orange jumpsuit and wears an Advanced Knee Replacement (also referred to as heel springs). It is revealed by GLaDOS that she is adopted. Her heel springs are destroyed when being dragged back into Aperture Science by the Party Escort Bot. Not much is revealed of Chell in Portal.
Lab Rat
In Lab Rat, it is revealed that Chell was originally rejected for testing. However, Doug Rattmann put her at the top of the list in hopes that she would be able to kill GLaDOS and help him escape. After, Rattmann feels bad about using Chell and saves her by giving power to her stasis chamber, but putting her in stasis indefinitely in the process. Chell's last name is redacted in the testing list.
Portal 2
Chell is awoken by an unknown person/system for a calibration test. She is then instructed to go back to sleep.