Newt Gingrich at Time's Person of the Year panel. Credit: Jemal Countess/Getty Images

Former Republican presidential candidate Newt Gingrich happened to be in Indiana on Monday when he asked his driver where he should stop for lunch. "The driver said St. Elmo Steakhouse," Gingrich told ABCNews.com. "And when I walked inside, I saw Rob Lowe."

Lowe was in Indianapolis filming an upcoming episode of his NBC sitcom " Parks and Recreation," which also stars Amy Poehler, who did not make the trip to Indy. The sitcom is set in fictional Pawnee, Ind., and the cast and crew were in town for a few days filming scenes about a bachelor party the characters take, which included a meal at St. Elmo.

An appearance by Gingrich wasn't in the script, but that all changed when he walked through the front door.

"We don't open until 4:00 p.m., but the doors to the restaurant were wide open and packed all day Monday because of the shoot," Bryn Jones, St. Elmo's director of marketing, told ABCNews.com. Jones assisted the "Parks and Rec" crew while they were on location.

"When one of the gals on our staff looked over and saw Gingrich, we made the assumption that he was here for the shoot. But, then the producer gave me a confused look," he said.

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According to Jones, the writers and producers quickly realized this was too good an opportunity to pass up so they huddled together, writing up a short scene for Gingrich where he played himself.

"It was great fun," said Gingrich. "Always fun to do something like that. I had a small role on a Candice Bergen show many years back."

Gingrich said he's "intrigued by American entertainment" and had a good time with the cast.

"It was especially great chatting with Rob Lowe. We have a mutual interest in General Grant and the Civil War."

Lowe also seemed to enjoy Gingrich's unplanned visit, saying on Twitter, "Latest surprise drop by on set: Speaker Newt Gingrich! So we made up a scene and put him in!! #AllHappeningInIndy"

Gingrich, who's never seen the sitcom, reportedly spent 90 minutes at the restaurant, where he eventually did eat lunch.

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He's not the first politician to have a cameo on "Parks and Rec." Vice President Biden appeared on a recent episode; Sens John McCain, Olympia Snowe, and Barbara Boxer have guested as well.

St. Elmo's is no stranger to serving celebrities and has been a downtown Indianapolis landmark since 1902. But, the staff said Monday's day of filming had special meaning.

"There are several of us who are pretty big fans of the show," Jones said. "It takes place in small town Indiana so there's ties to the towns our staff and friends grew up in."

Filming wrapped in Indianapolis on Monday night and show co-creator Michael Schur tweeted that the episode would air in January.