In the Aridor slave rescue game, credit chicks are the handful of very attractive but relatively weak and stupid women characters who are easy to win and who also make a lot of money (credits) for the characters who win them if assigned to a job requiring attractiveness. The current top 10 are nearly all credit chicks. In routine play, credit chicks are often "swapped", i.e. players quickly steal them from one another to make lots of money quickly.
The main credit chicks are Mariah Carey, the four Halliwells (Prue, Piper, Phoebe and Paige), Chellina (Gilina) off Farscape, Goodnight (from one of the Bond films) and one or two others - although these top ranking characters are not always the highest-earning or the easiest to get.
Some players also mention "credit dudes" - male characters with similar earning power - but the highest-scoring men are high-ranking in all three attributes and therefore very hard to win, so aren;t swapped much.
If someone steals Jean Grey from Enigma, he BGs the credit chicks and gifts them to other people.
I swapped credit chicks with Yuriko for half an hour to get my credit score up.