Stella is a dermatologist and single mother. Her worklife, combined with her bad experiences with men have caused her to steer clear of dating for over 5 years. She lived in New Jersey up until she remarried her ex-husband Tony, where she moved to New York.
After breaking up with Robin, Ted got drunk and woke up with an embarassing tattoo. He then went to Stella to get it removed and found himself attracted to her. Stella wared Ted that she refused to date her patients, but as the removal procedure took 10 visits, Ted plays this to his advantage and uses each visit to endear himself to her while still keeping her at arm's length. Stella finally gave in when Ted surprised her with a 2-minute date. She then agreed to be his girlfriend.
Ted was surprised to learn that Stella hasn't had sex in five years since since she had Lucy, but Stella slept with him even after finding out he shared the secret with Marshall and Lilly. Stella invited him to her sister's wedding in six months, but Ted turns down the invitation and presumably broke up with her. Their argument didn't stop Stella from visiting Ted after he got into a car accident. She leaves him when informed of his earlier intentions during the argument, but Ted refuses to give up on their relationship and proposes to Stella. It wasn't until they got engaged that Ted realised he didn't know enough about Stella. They soon found out how little they had in common, but persisted at the relationship, believing that love takes work. When Stella's sister cancelled her own wedding, they saw it as an opportunity to get married. On the day of the wedding, Stella got angry at Ted for bringing his ex-girlfriend Robin, saying it would bring up unresolved feelings. Ted tries to disprove this by inviting Stella's ex Tony. When Ted's back was turned, Stella left him for Tony.
Stella met up with Ted some time afterwards. The last time they spoke, Stella told Ted that the right one was coming, but he wouldn't know when or where, managing to establish some peace between them.
Tony was Stella's ex-husband. They had a daughter together, but Tony wasn't reliable enough, so she left him. Years later, Stella and Tony were reunited at her wedding to Ted. Their unresolved feelings got the best of them and they wound up running away together. Tony would later offer Ted a teaching position at local college as a way of apology, but this was later revealed to be a way of clearing his conscience. Tony would later make a film about their love-triangle where he was the hero and Ted was the villain.
Stella and Robin didn't have any real hostility towards each other, but when the wedding came up, tensions began to rise. Stella felt insecure being reminded that she was marrying someone else's hand-me-down, while Robin felt like a failure watching her ex getting married while she was left behind. Robin warned Ted that she might have lingering feelings that would make it hard to watch him get married. She also said that she thought Ted was rushing this relationship and disappearing into someone else's love life.