Robert Downey Jr. and Pedro Pascal's Halloween costume might hide a major

Robert Downey Jr. and Pedro Pascal spent Halloween dressed up as each other's Avengers: Doomsday characters. But that's not the headline here (although it certainly could be).

Instead, a Doctor Doom detail on Pedro Pascal's sweatshirt could clue us in further to the history between the new MCU supervillain and Reed Richards.

As seen below, Pascal's Doom sweatshirt sports an MIT logo with both Doom and Reed Richards adorning its emblem, perhaps suggesting they spent much of their college-age years together before growing apart and becoming bitter enemies.

Framing Doom and Richards, AKA Mr. Fantastic, as college rivals and mega brains is nothing new – and can be seen frequently in the pages of Marvel's comics.

But it certainly helps matters in the MCU. So far, we know precious little about how they are connected, and that always felt like one of Fantastic Four's missed opportunities last year. At once, it makes their rivalry more personal and tragic – and could sow the seeds for emotionally charged scenes between the pair in Avengers: Doomsday.

Doom was at least on the radar of Sue Storm in her role as leader of the U.N.-like Future Foundation, but the Latverian ruler was notably absent from the assembled nations in Earth-828's retro-futuristic 1960s.

The Fantastic Four post-credits scene at least brought Doom onto the scene, breaking into the group's headquarters and taking a keen interest in Reed and Sue's son, Franklin.

What happens next remains to be seen, but previous Doomsday footage has focused on the dynamic between Doom and Reed as a mutant-destroying Sentinel looms large in the distance. We bet they didn't teach that at MIT.

Avengers: Doomsday releases in UK cinemas on December 16 and in the US on December 18.

For more, we have guides on upcoming Marvel movies and how to watch the Marvel movies in order.