Irene being inspired by Erinyes? - (darklite)
Manifestation of Diane's moral
Why does the elderly couple emerge from the paper bag that the monster has placed on the ground? It’s because, in their miniaturized forms they have
"emerged" from the blue-box. Just as part of the secret in the dream
"leaked out" in the form of the triangular shaped key – these two little people are something from Diane’s Deep River Ontario past. They are part of her superego, or conscience. Those in our family, whom we get our morals from become internalized into our sense of self, and become part of our conscience.
I get the feeling that this couple is a part of Diane's superego in overdrive. They induced so much pride in Diane after winning a small-time dance contest, that she foolishly went against the odds and tried to parlay that into a Hollywood career. Perhaps the couple is a projection or amplification of the judges who showered Diane with compliments about her dancing. Diane then took these compliments to a grandiose extreme. When she faced the harsh realities of Hollywood (being one of many starving actresses who fail to be accepted into the realm of the superstars), her dream imploded on her. Manifestations of this implosion are a failed relationship and failure to realize her 'potential' as an actress. When Diane is at her wits end in the final 10 minutes, it is fitting that this couple (the reason she ended up in this mess) are there to drive her to take the life that they helped to ruin. - (KShermock)
Her parents may have died when Diane was young, and Irene and the older gentleman were based on the grandparents who raised her. With "parents" born two generations before, I bet such a child would have issues and unrealistic expectations of how easy it would be to succeed. And before her suicide, in the moment of her greatest desperation and psychosis, Diane would have matched her feelings with the way the thought of her grandparents made her feel at that time. - (Trichome)
"Another example of Diane's refusal to accept responsibility is revealed in an odd scene early in the movie that is part of Diane's dream. Betty has just arrived in Los Angeles with an elderly couple, Irene and her companion. As Betty takes a cab to her aunt's apartment, the couple are shown in a limousine laughing, eyeing each other knowingly, while Irene slaps the gentleman on the leg three times. They have the look of two people who have just pulled off a great gag or scam and gotten away with it. This couple is never identified, but they are seen with Diane onstage during her Jitterbug contest win in Ontario - the win she used as a stepping stone to get to Hollywood. When things didn't work out the way Diane had hoped, she concludes that she was the victim of some scheme by the seemingly kind couple.
Diane believes she's done everything right, played by the rules, yet outside forces have conspired against her, resulting in her failure - even to the point of her belief that the elderly couple who accompanied her from Canada set her up for failure."
Irene and her companion represent some sort of parental figures to Diane - moral
centers who would instill and drive her guilt for committing a monstrous crime.
Their representation though is also mirrored by society seeking justice
and hence would be the “two detectives” seeking out Diane and bringing her
to social justice.
My guess is that Diane ran away from home to escape her parents/grandparents. Given the name of her town (Deep River) basically means "deep water" I think there is a suggestion that she was "out of her depth" or otherwise in trouble there. Coming to L.A. in reality hasn't worked out (to put it mildly). So in her subconscious, she tries to put everything right, saving Rita, having a perfect relationship with her, having Adam ruined, having her relationship with the old people be perfect. At the end, the old people are chasing her and terrifying her because they are a symbol of a crushing reality rushing back in. That's why they are coming out of the box which is opened with the key - the key signifying knowledge of Rita's murder. At that point it is too late, and she can't keep up the idyllic dream. She can't stay in L.A. because "those detectives" are on the trail, and if she does go back home it will be an admittance of failure, and to an unhappy environment. At that point, suicide seems the only escape. - (NxNWRocks)
Maybe the couple are some slim metaphor for the false kindness Betty has found in L.A.; i.e. being kindly on their journey and initially wishing her well, but as soon as she turns away - they almost seem to be mocking her with their eerie smiles. They represent the evil of the city and in the end they come to taunt her.
Although she tried to repress the memory of the abuse, Diane's relationship with her grandparents never recovered, and
she did not feel loved by them. But when she got older, something happened that helped to produce a new and more pleasant dimension to their difficult relationship. When Diane was a young adult, she won a Jitterbug contest in Canada. Her grandparents were very happy about this and they seemed to suddenly believe in her again. It was as though she could win their love back as long as she was a star. They even encouraged her to pursue her dream to go to Hollywood.
Adam and Camilla
We see the old couple grinning maniacally in the limo. Not only do they look like two people who have just set a trap and are reveling in a bit of revenge, they are also reminiscent of Adam and Camilla laughing uncontrollably at the party as they try to make their announcement. Remember their announcement led directly to the scene where Diane hires the hitman. Also notice the similarities between Adam's glasses and the old man's glasses.
Finally, at the end of the movie the monster behind Winkies sets down a paper bag. Inside the bag we see the blue box, some raw meat (death), and a beverage can's tab (something's been opened …). Then the old couple crawl out of the bag. They are on their way to Diane's to seek vengeance because she had them murdered. They - are Adam and Camilla. - (fornus)
Trivia: Jeanne Bates (the actress playing Irene) also played Mary's mother in "Eraserhead". She passed away November 28, 2007, aged 89.