The Avengers and slowly revealed the truth behind his resurrection during season 1. This included the reveal that Coulson's memories were altered to forget the gruesome, experimental operations it took to bring him back to life.
With the launch of WandaVision on Disney+, the MCU's first Phase 4 show sets up a similar mystery at its core. Wanda Maximoff, a.k.a. Scarlet Witch (Elizabeth Olsen) and Vision (Paul Bettany) are living in a fake world that mirrors different TV sitcoms. They attempt to blend in, but there are plenty of signs that there is something strange with this new life. During the first episode, this includes an odd moment where one of the characters repeatedly yells stop. For Agents of S.H.I.E.L.D. fans, this might feel quite familiar.
The episode includes Wanda and Vision hosting his boss, Mr. Hart, and his wife for dinner. The night takes a turn for the worse when Mr. Hart begins choking after asking too many questions. This leads Mrs. Hart to repeatedly say "Stop it," with her tone changing from light-hearted to fearful as it slowly dawns on her he's not playing around. She initially directs this to Mr. Hart before turning to Wanda and asking her to help Mr. Hart. In Agents of S.H.I.E.L.D., Coulson's altered memories of his "trip" to Tahiti found him getting a massage and saying "Don't stop" to the masseuse. In reality, he had been pleading, "Don't. Stop." to the doctors operating on his brain while he was awake. While this could be coincidental, Mrs. Hart telling her husband to stop what he's doing and growing progressively angrier as he continues could potentially be Wanda's interpretation of experiments that are happening to her in the real world.
The mystery behind WandaVision's fake reality is still being unraveled, but many fans think Scarlet Witch is responsible for this world. However, there is a real possibility that someone is messing with Wanda in the real world, and this life is a projection to keep her powers under control. Episode 2 includes the introduction of Monica Rambeau as "Geraldine," which could be a sign that no one in this world is who they say they are. If that is the case, then Mr. and Mrs. Hart could also be behind what is happening. In Agents of S.H.I.E.L.D., Coulson's memory was altered so the doctors he saw were replaced by a bartender and a masseuse. Perhaps Mr. and Mrs. Hart aren't who they appear to be, either. This would explain why they are the first ones to question Wanda and Vision and why they leave so quickly after potential danger.
With WandaVision's fake world potentially having a similar effect on Wanda as Agents of S.H.I.E.L.D.'s Project Tahiti had on Coulson, it will be fascinating to see if any other connections are made. It is highly unlikely that Project Tahiti will be referenced by name, but what is happening in WandaVision could be an extension of it. If Fury and S.H.I.E.L.D. figured out how to change Coulson's memory, someone else might have discovered a way to make subjects believe they're actively living a different life. If Wanda ever refers to Westview as "a magical place," WandaVision's connections to Agents of S.H.I.E.L.D. will be all but confirmed.