Mitt Romney, peppy and even silly, popped up unannounced Saturday at his campaign headquarters here, where he rallied volunteers by telling light-hearted stories about his family and even offering to autograph his supporters’ bare arms.

“Just undo your shirt and we’ll sign your arm,” Romney joked.

Romney is a habitually upbeat presidential candidate, but he seemed particularly so Saturday, just hours before taking the stage at Drake University here for his first debate since former House speaker Newt Gingrich surged past him to a commanding lead in the polls.

On Friday night, following a few hours of debate preparation here with his top advisers, Romney said he relaxed by retiring to his hotel room with his wife, Ann, and their 35-year-old son, Josh. Romney told reporters they watched “The Help,” which he said he picked up at RedBox, and called the film about black maids in 1960s Mississippi “very powerful.”

Romney continued his debate prep sessions Saturday morning before driving over to his campaign headquarters, an old Blockbuster Video store on the outskirts of downtown Des Moines. He made a surprise appearance at what his campaign billed as an event featuring Ann and Josh Romney, as well as a top campaign surrogate, former Minnesota governor Tim Pawlenty, and his wife, Mary. Mitt Romney joined them on stage to address nearly 100 volunteer supporters, and lingered for a while to greet them individually.

Pawlenty, who backed Romney after ending his own campaign this summer, offered a full-throated endorsement and, without mentioning Gingrich, continued a line of contrast begun by Romney’s campaign this week.

“When we elect a president of the Untied States, the person who sits in the Oval Office at that desk and makes decisions about the future of our country, sometimes very important and heavy decisions, we need a person in that chair who we know has a steadiness, who we understand has an experience and a knowledge and a wisdom that’s tested throughout his or her life and make sure that they have the kind of judgment and wisdom and capability to be president,” Pawlenty said.

“When you look at Mitt Romney’s and Ann Romney’s life, it’s a life of incredible commitment, of service, of good judgment, of wisdom,” he continued. “This person, Mitt Romney, is the most knowledgeable and capable and electable candidate in this field.”

Just over Romney’s shoulder, a white board showed just 24 days remaining until the Iowa caucuses, and Romney pledged to return here again and again. “We’re going to get to know you better and better over the coming weeks,” he said. “You’re going to see us time and again here in Iowa.”

Romney’s campaign has highlighted his family life in recent weeks. During his remarks, Romney introduced “this tall, good-looking guy next to me here” – Josh, third of his five sons, who in the run-up to the 2008 campaign visited all 99 counties to campaign for his father.

“He’s my hero,” Josh Romney said. “He’s the guy I look up to, he’s taught me everything I know, he’s taught me my great love for this country, and taught me my great love for my family. He set a great example.”

Mitt Romney went on to describe Josh’s “extraordinary talent.”

“Josh, at a very young age – he was maybe 4 – he was able to drop his voice like two octaves and when I’d grab him by the arm and rush him up to his bedroom, he’d turn to me and he’d say: ‘Don’t hurt froggy,’ ” Romney said. “I’d just bust up laughing. He’s never been punished.”