A popular online theory indicates Christoper Nolan’s high-concept sci-fi films Tenet, Inception, and Interstellar are all related, prompting a Nolan-connected universe outside of his Dark Knight trilogy. Nolan has a knack for mind-bending time and space-related scientific theories in his work, and these three movies are heavily entangled with these concepts. Inception, Interstellar, and Tenet share high-concept solutions for mankind, so the Nolanverse theory is a clever way to present fictional humanity’s worldwide struggles in an interconnected manner.
Inception (2010) stars Leonardo DiCaprio as Dom Cobb, a thief who, along with his team, steals information for clients from his victims’ subconscious. Interstellar (2014) features Matthew McConaughey as Cooper, who alongside fellow astronauts must find alternate, viable planets to save mankind from an apocalyptic Earth. Tenet (2020), Nolan’s latest film, stars John David Washington as The Protagonist, an agent tasked with manipulating time entropy to stop an attack from future villains on present humanity. An intriguing Nolanverse theory from Twitter user FILMDILFS connects Cobb’s Inception kids to the Tenet organization and Interstellar as the dystopian future from which Tenet’s first inverted characters and entropy technology come from.
The first part of the Nolanverse theory speculates that Tenet’s characters Neil - The Protagonist’s case handler - and Barbara, the scientist who first explains the time entropy of future objects, are Dom Cobb’s children from Inception grown up. Cobb’s children were very young during Inception, but the girl was obviously a few years older than the boy which does correlate to Neil being younger than Barbara. The characters also all have sandy brown hair in both movies, which is significant because Tenet’s casting description for Neil included a specification of light-brown hair (Robert Pattinson dyed his hair for the role). The connection furthers by Barbara clearly being French (played by French actress Clémence Poésy), and the children’s mother Mallorie was notably French (played by Marion Cotillard).
The Tenet and Inception link is a slight stretch unless the two kids ended up changing their names, considering they are called Phillipa and James Cobb in Inception, and Barbara and Neil in Tenet. Although, since there are no given last names for the characters in Tenet, it's entirely possible they changed their names following their mother’s death and Dom’s possible disappearance into a dream world. It also wouldn’t make much sense for Barbara to adopt her mother’s French accent while Neil has a British accent, unlike his American father. Unless the children were separated and raised in different countries, the Inception-Tenet link is pretty loose.
The Tenet-Interstellar connection is more plot-based, theorizing Interstellar’s setting of the apocalyptic Earth is actually Tenet’s future, wherein the Time Bomb was created to destroy Earth and humanity because it became uninhabitable in the future. Since Tenet’s Time Bomb was destroyed, the future Earth would still be at its uninhabitable end, which is exactly Earth’s fate in Interstellar. It’s possible The Protagonist from the future decided to mastermind “Tenet” and stop Sator’s Time Bomb because he knew Interstellar’s government entities like NASA were already working on ways to move mankind off Earth.
Considering Nolan tends to implement the concept of human crisis in his stories, Tenet and Interstellar (and by extension, Inception) may just be a shared theme of humanity’s end and different reactions to it, rather than an actual universe connection. The protagonists of Tenet (The Protagonist and Neil) and Interstellar (Cooper, Brand, and Murph) all take a more optimistic view that they can use high-concept science to save humanity from a dying Earth. They both face enemies to their near-hopeless missions; Tenet’s Sator takes matters into his own hands to create a Time Bomb and kill mankind, while Interstellar’s Professor Brand and Dr. Mann give up on humans already inhabiting Earth and sabotage the plan to save them. Audiences will have to wait for Nolan’s next sci-fi movie to see if Nolanverse connections are strengthened and confirmed.