[Editor's note: The following contains spoilers for Marvel's What If...?, Season 1, Episode 8, "What If... Ultron Won?"]
Episode 8 of Marvel's What If...? featured something along the lines of breaking the fourth wall on a literal level, as our extremely observant pal the Watcher (Jeffrey Wright) chose to observe a universe where things went more horribly wrong than usual. In this realm, the highly advanced A.I. developed by Tony Stark to protect the planet Earth once again resorted to extreme measures to fulfill its purposes, but this time was a lot more successful: as the episode title establishes, Ultron beats the Avengers, and goes on to also attack the Watcher, having evolved to a high-enough level of consciousness to be aware of the existence of multiverses, not to mention the Watcher himself.
In the film that this episode is based on, Avengers: Age of Ultron, the voice of the titular killer robot army was provided by '80s icon and prolific film and television actor James Spader. Perhaps Spader was busy with The Blacklist (though when that show did a quasi-animated episode at the beginning at the pandemic, he did manage to take the time to play his character in that), perhaps he simply wasn't asked — but the actor who did fill in as Ultron has a very unique set of experiences when it comes to playing characters originally played by other actors.
Ross Marquand is both a veteran screen actor, perhaps best known as zombie apocalypse survivor Aaron on AMC's The Walking Dead, as well as an established voice actor for shows including Robot Chicken, Invincible, and Family Guy. But he made his MCU debut by stepping in when Hugo Weaving didn't return as the character of Red Skull in Avengers: Infinity War. Red Skull, now serving as the entity in charge of looking after the Soul Stone on Vormir, was a key figure in that film as well as Endgame, which meant work for Marquand in both films... plus also What If...? Episode 1, "What If... Captain Carter Were the First Avenger?", in which he also played Red Skull (albeit in his earlier, more Earth-bound state).
Marquand being tapped here to fill in for Spader might have come as more of a surprise if this wasn't his first time playing Ultron. In the 2019 video game Avengers: Damage Control, he also played the character alongside returning MCU veterans including Paul Rudd as Scott Lang/Ant-Man, Letitia Wright as Shuri, Evangeline Lilly as Hope van Dyne/Wasp, and Benedict Cumberbatch as Stephen Strange/Doctor Strange.
Now, not only has Marquand fully embodied the role, but he's also poised to be a central figure in next week's season finale, the title of which is as yet currently unknown, but seems very likely to feature the Watcher getting his chance to take Ultron down, with some help from Doctor Strange as well as maybe other survivors of previous What If...? tales. The possibilities aren't technically endless, but the boundaries are only found in the potential of the multiverse as a concept, as well as the imaginations of the writers. Which is to say, there are a lot of options for what might be in store.
The season finale of Marvel's What If...? premieres next Wednesday on Disney+. Previous episodes are streaming now.