The excitement surrounding Avengers: Doomsday has only grown since Marvel Studios unveiled its massive cast at San Diego Comic-Con. With legacy Marvel stars joining forces alongside the MCU's biggest heroes, fans have been eager to learn what it was actually like behind the scenes. As the franchise brings together actors from multiple eras of Marvel storytelling, even the cast has found itself overwhelmed by the scale of the crossover.

While Marvel continues to keep the film's biggest plot details under wraps, Robert Downey Jr. recently shared a candid moment from the set that perfectly captures the excitement surrounding the crossover. His comments offered a glimpse into one reunion that left even the veteran MCU cast in awe.

During Entertainment Weekly's post-Hall H interview at San Diego Comic-Con, Robert Downey Jr. reflected on what it was like sharing the Avengers: Doomsday set with original X-Men stars Rebecca Romijn and Kelsey Grammer. The moment underscored just how significant the multiversal crossover has become, bringing together actors who helped define Marvel on the big screen long before the MCU existed.

"I have to say, we nerded out," Downey Jr. said while speaking about Rebecca Romijn and Kelsey Grammer's return as Mystique and Beast during Entertainment Weekly's post-Hall H interview.

Referring to fellow Avengers: Doomsday cast members in the Entertainment Weekly interview, Lewis Pullman, David Harbour, Paul Rudd, Chris Evans, Letitia Wright, and Pedro Pascal revealed just how excited everyone was to share the set with the original X-Men stars. Although he avoided discussing the duo's roles in the film, Downey Jr. admitted their presence "lit up this constellation of excitement," highlighting how meaningful the reunion was for the cast.

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That was not the only recent moment in which Robert Downey Jr. hinted at Doctor Doom's mindset outside the film itself.

Ahead of Avengers: Doomsday, Robert Downey Jr. also sparked conversation with a Father's Day post shared back in June. The hand-drawn illustration featured two crossed-out kites, each carrying a familiar Marvel symbol that immediately caught fans' attention. In the Father's Day illustration, one kite featured the Avengers logo with a red prohibition symbol, while another carried the Fantastic Four emblem marked the same way.

Rather than presenting Doom as an outright menace, the playful, childlike artwork injected humor into his iconic rivalries with both superhero teams. Released not long after Fantastic Four: First Steps brought Marvel's First Family into the MCU, the post also appeared to subtly hint that Avengers: Doomsday will see Doctor Doom facing heroes from multiple corners of the Marvel universe.

As Marvel continues teasing Avengers: Doomsday without revealing its biggest secrets, moments like Robert Downey Jr.'s heartfelt praise for the original X-Men cast and his subtle social media nods have only fueled anticipation for what promises to be one of the MCU's most ambitious crossovers yet.

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What are you most excited to see in Avengers: Doomsday, the return of the original X-Men or Robert Downey Jr.'s Doctor Doom? Let us know in the comments!