But when an agent from New York's Waxman Literary Agency asked him to sign with the firm, he realized it was time to fess up.
"I was super nervous. I was especially nervous because I talked to my brothers," Halpern said. His oldest brother, he said, laughed until he cried and then told him he should think twice before telling his dad.
But, good son that he is, Halpern realized he couldn't pursue a book deal without his father's blessing.
So he braced himself for the worst and started to explain their newfound Twitter fame. When his dad asked, "Do you have to start up the Internet to get on Twitter?" he knew he was in the clear.
After laughing for about 10 seconds, Halpern said his dad asked him to help find his cell phone.
"I felt better," Justin said. "He had moved on."
When he told his father about the book, Sam had two stipulations: No interviews and no money.
"I don't want any money. I have my own," he told his son.
It's that kind of charming churlishness that Halpern's new agent hopes will sell books.
Byrd Leavell, an agent with Waxman, said they're still tossing around ideas for a book but explained that it will likely be more than just a compilation of Tweets.
"Right now, I think that there are a lot of prescriptive life's little instruction books out there, but there aren't any done in the voice of Sam," he said describing one possibility. "It could be a lot of fun to take a spin on that approach."
Given the response from Halpern fans around the country and across the world, it seems that the voice of Sam is one people are indeed seeking.
Kristie Aylett, a 41-year-old public relations consultant in Ocean Springs, Miss., started following Halpern's page a couple of weeks ago after one of her friends forwarded a Twitter message about it.
On Thursday, she posted herself: "I must be homesick. I can actually hear family members' voices ..."
"Once I found the feed, then it just made me laugh," Aylett told ABCNews.com. "It reminded me of my grandfather, who's been dead for years."
Sam Halpern's comments, she continued, recall a time of candor and frankness that's long gone.
"In this day of political correctness … that pure, honest expression is getting rarer and rarer, and I think that's what spoke to me," she said. "You know where you stand with this kind of person and whether they're telling you to toughen up."
Even Little Leaguers and his offspring aren't spared from Sam's tough love:
"These kids are all fat," he mused while watching the Little League World Series recently, before turning his attention back to his son. "I remember when you were in Little League. ... You were fat."
Chris Brogan, president of New Marketing Labs, a new media marketing agency, and co-author of "Trust Agents: Using the Web to Build Influence, Improve Reputation and Earn Trust," said "emotional resonance" is at the core of why Halpern's Twitter page took off.
He, too, can remember a family member who became a legend for her embarrassment-inducing level of frankness. And he said he suspects many other fans can too.
"This thing is built on two really powerful switches," he said. "[It's] easily sharable with emotional benefits to it, and it reminds us, in a nostalgic sense, of a relative."