- “This was a good breakfast, Beth. You really made the crap out of those eggs. I wish your mother was here to eat them.”
- —Rick referring to his ex-wife.[src]
She has never physically appeared in the series, and her real name, appearance, and fate remain unknown, although references to her suggest she may be deceased.
In the pilot episode, Rick compliments Beth: "This was a good breakfast, Beth. You really made the crap out of those eggs. I wish your mother was here to eat them." The comment brought a tear to Beth's eye, and the use of past tense suggested that Mrs. Sanchez has died.
In "Rick Potion #9", Rick reflects on his marriage indirectly when he informs Morty that "Love is just a chemical reaction that compels animals to breed", mentioning that he was also part of a failing marriage, much like his daughter and son-in-law. He then encourages Morty to break the cycle and focus on science. Beth (C-137) later mentions that Rick indeed left her mother.
At the conclusion of "Auto Erotic Assimilation", Beth insists to Rick that she "can't sacrifice this whole family's safety just because I'm afraid you'll leave again," and then realizes that she sounds like her mother, suggesting that Mrs. Sanchez valued her family's safety over Rick's scientific experiments.
In episode "The ABC's of Beth", Beth ask Rick why would he made a clone of her so she can have some time for herself. He states that it might be something about her mother. It indicates that Rick possibly still loves his ex-wife.
Main Article: Diane Sanchez
When Rick was being held in a Galactic Federation prison, Cornvelious Daniel went into Rick's memories, via a brain-link, to retrieve how Rick became a criminal. While Daniel was present in Rick's memories, he witnessed a flashback where a younger Rick was married with a woman named Diane Sanchez, along with their daughter Beth, is visited by another Rick from the future, who sends back a bomb to vaporize Diane as well as Beth. The 'present' Rick reflects later in the episode to Morty (who had seen none of it) that he was not driven by a "totaly fabricated origin" backstory, indicating the one he had shown earlier.
Although Rick had no reason to lie to Morty, given the latter was never present for the scene, some elements of the story are speculated to be true, such as the possibility that Rick may not have been native to Dimension C-137 and adopted that Beth and her family after having lost his own. He has also shown a grudge against the Council of Ricks and other Ricks, and mentioned "payback" in "The Rickshank Rickdemption", although this may have in reference to his failed assassination in the episode or his previous encounter with them. It may also be notable that Diane appears to enjoy Rick's scientific work and seems very patient and understanding, with no reference to a "failing marriage" or anger about safety.
It can therefore not be guaranteed that the flashback represents Rick's backstory or who Mrs. Sanchez really was or how she appeared.
Behind the Scenes
The absence of Mrs. Sanchez has been noted since early in the series, with very little being discussed about her, even by series creators. Dan Harmon has said on multiple occasions that she is "unremarkable", later suggesting she was more comparable to Jerry, and that this manifested in Beth's idolization of Rick.
In "Close Rick-Counters of the Rick Kind", Rick is shown with a memory of having sex with an unknown blonde woman that some speculated was his wife, although this suggestion was shot down.
Giahna Pantano, cover artist on Oni Press' Rick and Morty comics, created a non-canon character named Bonnie Sinclair to serve as a hypothetical wife for Rick, and art featuring her became popular with fans, though her characterization differs from what the series suggests for Rick's ex-wife.