Patrick Leahy has been in the Senate for decades. But a cameo in this Batman movie was a highlight.

Sen. Patrick Leahy, the veteran Democratic lawmaker who told reporters Monday he will not seek re-election in Vermont, holds impressive distinctions. He is the longest-serving sitting U.S. senator. He is third in the line of succession to the presidency.

He is also the only member of the U.S. Senate to make cameo appearances in five Batman films.

Leahy, who has said he first started reading Batman comic books as a young boy at the Kellogg-Hubbard Library in Montpelier, made his first Batman film cameo 26 years ago in "Batman Forever" (1995), starring Val Kilmer.

The same year, Leahy voiced a character in "Batman: The Animated Series," a popular show that put a darker spin on Gotham City's masked crusader.

Leahy went on to appear in "Batman & Robin" (1997), "The Dark Knight" (2008), "The Dark Knight Rises" (2012) and "Batman v Superman: Dawn of Justice" (2016).

In that last movie, he played a character named Senator Purrington and acted alongside Holly Hunter.

"The Dark Knight" gave Leahy his juiciest role outside Capitol Hill — as well as his most cherished Batman cameo, according to David Carle, Leahy's press secretary.

Leahy shows up in the seminal Christopher Nolan thriller as a sharply dressed partygoer who confronts Heath Ledger's Joker and says, "We're not intimidated by thugs."

"You know," Ledger's Joker famously responds, "you remind me of my father. I hated my father." The Joker then menaces Leahy's character with a knife.

Leahy has praised Ledger, who died before "The Dark Knight" hit theaters and won a posthumous Oscar for his career-defining performance.

"He scared the heck out of me, when he came at me with the knife," Leahy told the political publication Roll Call. "I didn't have to act."

Leahy, paying tribute to the place that first led him to the Batman comic books, donates his cameo fees and royalty payments to his hometown Kellogg-Hubbard Library in Montpelier, Carle confirmed.

He has also written the introductions to two DC Comics anthologies.

It was not immediately clear what Leahy's departure from the Senate means for his sideline gig as a film actor.

He told the Burlington Free Press last year that he "didn't even seek to be in" the upcoming Batman franchise reboot starring Robert Pattinson.

"I have too many other things going on with Covid, with appropriation bills," Leahy told the newspaper in August 2020.

But what about future installments?

"We'll see," Leahy's press secretary said in an email.