The Three Huge MCU Stars You Likely Forgot Starred On Seinfeld

Comedian and actor Jerry Seinfeld's self-titled 1990s sitcom "Seinfeld" is one of the most well-known television shows of all time. It had a nine-season run, first airing back in 1989 and ending in 1998. Its biggest competitors were, of course, "Friends" and "ER." According to Entertainment Weekly's reports on viewership during the height of each show's popularity during 1996, "Seinfeld" drew a total of 33.24 million viewers, with "Friends" following behind at 28.98 million.

Although, the argument could be made that "Friends" was still in its infancy, as the show only premiered two years prior in 1994. Either way, that's a lot of viewership for any NBC show back in the 1990s. Like "Friends," the popularity of "Seinfeld" is so great that it is still re-run on various television networks to this day, many years after "The Finale" two-part ending.

Popular television series, whether it's sitcoms or crime shows, often serve as a proving ground or showcase for the up-and-coming talented young actors and actresses in Hollywood. "Law & Order" is famous for this, but some people may not know that "Seinfeld" also served as a jumping-off point for modern Hollywood stars — including some well-known characters in the Marvel Cinematic Universe. Here are the three big MCU stars that you likely forgot made their appearances on "Seinfeld" when the sitcom was at the height of its popularity.

Before he played a massive part in laying the foundation for the Marvel Cinematic Universe in 2008 with "Iron Man," Jon Favreau was still landing plenty of acting roles in the 1990s. This was years before he would decide to give Robert Downey Jr. a shot at playing Tony Stark, and we all know how that went. Favreau notably directed "Iron Man" and "Iron Man 2," along with starring as Tony's bodyguard and arguable best friend, Harold "Happy" Hogan. His character of Happy still plays an important role in the MCU, as we were able to see Favreau reprise his role in "Spider-Man: No Way Home" most recently. However, before playing Happy or getting in the director's chair, Favreau had a small part in the "Seinfeld" episode titled "The Fire" as Eric the Clown.

During the episode, George (Jason Alexander) is asked by his girlfriend at the time, Robin (Melanie Chartoff), to hire a clown for her son's birthday party. George ends up hiring Favreau's Eric, who makes it clear that being a clown is just a side gig for him and not his real passion. In conversation, George gets upset that Eric doesn't know who Bozo the Clown is, and they have an altercation until sometime later, the apartment is set on fire. Robin then breaks up with George due to his choice to flee. Although Favreau plays a small and humorous part in this episode, Robin and George's breakup was a bigger event in the series.

Veteran actor James Spader became a part of the MCU back in 2015's "Avengers: Age of Ultron" as Tony Stark's backfired albeit well-intentioned AI, Ultron. Although Spader's physical form is never seen for obvious reasons, his voice gave emotion and life to Ultron's deep-rooted and misguided views on humanity and the purpose of life. Although the actor did not return to voice Ultron in the recent Disney+ series, "Marvel's What If...?" (via Collider), he joins the list with Favreau as another MCU actor who appeared on Seinfeld.

Spader played Jason Hanky in the Season 9 episode titled, "The Apology." Spader's Hanky is a childhood friend of George's who is going through rehab for alcohol addiction. As part of the steps to recovery, Jason begins to apologize to people that he had wronged or been unkind toward in the past. George thinks he deserves an apology from Jason, specifically for an insult that he made a few years earlier about a sweater he did not want to give to George due to his large head. Jason ultimately refuses to apologize, leading George to be recommended to an anger management class by one of Jason's sponsors.

It's a hilarious episode and a coincidence that again one of the guest stars, like Favreau, played a role in George's story. During the time of Spader's appearance, he was coming off of feature films like "Stargate" and "Critical Care," although he is most known for his role as Raymond Reddington on "The Blacklist" (via IMDb).

Patton Oswalt is one of the busiest actors in modern Hollywood, having over 226 credits on his resume. One of his first official acting jobs was on "Seinfeld." Oswalt appeared briefly during the Season 6 episode titled "The Couch," and his time, like Spader and Favreau's, is spent on George's storyline.

During the episode, George joins a book club in an effort to impress his current girlfriend, and the book they chose to read is "Breakfast at Tiffany's." It was famously adapted into a film as well, and George has trouble reading the book so decides to try and rent the movie instead. This is where we meet Oswalt, the clerk, who informs George that their copy is already rented out and he can't give him information on the customer who rented it.

It's a very quick scene, and a small role for a well-known actor like Oswalt nowadays. In the MCU, Oswalt is a fresh face although he has been a part of multiple projects with Marvel, including "Marvel's M.O.D.O.K." and the "Spider-Man" series on Disney XD. He appears in "Eternals" at the very end of the film during a post-credits scene with Harry Styles' Eros/Starfox as Pip the Troll.

As more information is released surrounding a possible "Eternals 2," we will have to see what the future holds for Oswalt. For Favreau and Spader, their next appearances are more uncertain, although anything is possible in the MCU.