SPRINGFIELD -- At the Basketball Hall of Fame’s 60 Days of Summer program, each appearance has a format: A Q&A with the player, followed by a few questions from kids, followed by an autograph session.

On Monday, as the kids’ Q&A wrapped up, there was a minor stampede for the autograph line. The bleachers emptied as the speaker answered a final question, and people hurried toward a growing queue which snaked around the Hall of Fame gymnasium.

Boston Celtics big man Tacko Fall is a popular guy these days. Without looking at official numbers, Hall of Fame staffers guessed (with some confidence) his crowd on Monday was comfortably the biggest of a summer that included Boston’s lottery pick this season, Romeo Langford.

As is often the case, the bigger crowd led to some strange autograph requests. One boy asked Fall to sign his iPhone. Another autograph seeker proffered a printed picture of a taco. A young man went through the line and had to double back when he realized Fall had accidentally signed a photo of former Kansas City Kings star Otis Birdsong, instead of the pre-made photos of Fall himself most fans received. A little girl wanted Fall to sign a tiny basketball, which nearly disappeared in Fall’s enormous hands. A young woman handed Fall a customized Celtics jersey with Fall’s name and number (55) on the back, which she said was a gift from her father.

All of this for a player who is yet to officially make the Celtics roster, but Fall (obviously) isn’t ordinary. At 7-foot-7 with an 8-foot-2 wingspan -- the longest wingspan ever recorded at the NBA combine -- Fall’s size makes him unique. As fans went through the line, most shook Fall’s hand, and seeing their hands disappear in his seemed to be part of the experience. One boy asked if he could put his hand up against Fall’s after receiving his signed picture, and Fall obliged. The boy’s entire hand fit comfortably in Fall’s palm, and the rookie closed his fingers around around the boy’s, pretending to trap it with a smile (Fall’s agent offered hand sanitizer at the end of the session, which Fall accepted gratefully).

“This one was definitely the longest (autograph line),” Fall said afterward. “Some of them had funny questions as well as they were passing by. They made it fun for me. I wasn’t just sitting there.”

In his first question with interviewer Kyle Belanger, Fall told an anecdote about posting a photo of the Hall of Fame to social media a few years ago when he was just starting to play basketball with the caption “One day.”

“That’s a true story, true story,” he said, as the audience applauded. “God works in mysterious ways, and now I have the chance to play this game that I love at the highest level and inspire so many other people, and I feel really grateful.”

Fall’s popularity spiked at Summer League, where he looked more mobile and fluid than one would expect for a player his size. After he went undrafted in June, the Celtics inked him to an Exhibit 10 contract -- a minimum salary deal that guarantees an invitation to training camp. If Fall is waived from his Exhibit 10 deal, he will be offered a $50,000 deal to join the Celtics’ G-League team.

But the Celtics have an open roster spot, which could either go to Fall or to guard Tremont Waters, opening up a two-way deal for Fall. He will be competing with Javonte Green -- another Summer League standout -- but if the enthusiasm around him is any indicator, Fall’s jersey sales might be worth the roster spot alone, and his unique size and skill set could easily prove worth a flier.

After the event on Monday, Fall met Celtics Hall of Famer Tiny Archibald underneath the building, away from Fall’s crowd of fans. Archibald presented Fall with a commemorative basketball with his name, number and photo emblazoned on it. Archibald informed him there was a player from New York on the Celtics roster who he knew as a child. Fall couldn’t figure out which teammate Archibald was referencing, but he said he would look it up right away (the answer, of course, is new star Kemba Walker).

“It’s awesome,” Fall said of the Hall of Fame experience. “Just being in this environment with all those legends, being here with all these people.”

Fall, who is back from a trip to Senegal and working with teammates in Boston for the rest of the summer, said the Celtics organization gave him good feedback after Las Vegas.

“They’re very excited to have me, and they believe in me,” Fall said. “That’s something I wanted. I wanted to be in an environment where I feel like people want me there and believe in me. I feel like the organization believes in me. It’s a great vibe going on, great players, so I’m really excited and looking forward to the future.”