New Batman Ben Affleck Makes Guest Appearance at Superman-Themed Birthday Party

The star is currently filming "Batman V. Superman: Dawn of Justice" in Detroit.

— -- A rivalry of heroic proportions has intensified this summer as Ben Affleck shoots 'Batman v. Superman: Dawn of Justice' in Detroit, MI. But an unexpected chapter in the contest unfolded over the weekend.

On Sunday, Affleck, 41, who plays the caped crusader in the forthcoming Warner Bros. film, crashed a child's Superman-themed birthday party.

Together with wife Jennifer Garner, 42, and son Samuel, 2, Affleck had dropped by Detroit Kid City in Southfield for a morning of family fun. But the couple was told that the complex was closed for a private celebration.

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Garrett Dixon, of Detroit Kid City, told ABC News that the actors arrived roughly twenty minutes before the bash was scheduled to begin and asked if they could "just take a peek" inside.

After surveying the kid-friendly site, Affleck wanted to know whether his son could join in the festivities.

"You can't really pull a two-year-old back out of there after he's seen it," Dixon said. He checked in with the hosts, who were unsurprisingly happy to grant the A-listers entry.

"They ended up hanging out for about an hour and a half," said Dixon, who called the duo "very down to earth."

According to Dixon, Garner spent the time "mingling" with other moms while Affleck discussed the possibility of building a version of the miniaturized Motor City in Los Angeles: "They had a great time. I know it sounds cliche, but they were really just trying to enjoy this with their son."

The venue, which boasts a menu of locally sourced snacks and organic coffee, has proved its star power before. The Detroit Free Press reported that Mark Wahlberg brought his children to the indoor playground while filming Transformers: Age of Extinction in 2013.

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