Dean meets Anna during the fourth season, and protects her from angels and demons and soon discovers that she is an angel herself.
Anna is empathetic and sympathetic towards Dean for his undeserved suffering within Hell, and he feels he can relate to her unease of taking orders from an absent father.
During Heaven and Hell, they have a moment together and hook up for the night.
Dean protects her until the moment Uriel threaten Sam.
Whenever Anna pops in, Dean is surprised to see her, but treats her kindly.
They are on friendly terms until Anna goes back in time to kill Mary and John. Dean later witnesses her death at the hands of Michael.
Dean first met Cassie in Athens, Ohio, where she was at college and he was on a hunting mission.
When her father was killed, she contacted Dean for help and they eventually renewed their relationship by sleeping together, although Dean soon left town again.
In Dean's fantasy world, Carmen was his live-in girlfriend. She knew almost everything about him (his favorite beer and foods).
She also worked as a nurse and Dean was surprised he was dating a respectable woman.
In the real world, she was a model in a magazine for his favorite beer.
Dying from an inoperable brain tumour, Layla and her mother were frequent visitors to Roy Le Grange's church in the hope that he would heal her.
She met Dean and formed a friendship with him after he was healed, but Dean and Sam had to stop the 'miraculous' healings before Layla was cured.