WATERVILLE — He was in and out of the Alfond Youth and Community Center in about a half-hour. But this is Rob Gronkowski. He can cram a lot of excitement into a half-hour. Not one second was wasted.

The former New England Patriots tight end (and maybe future tight end, if rumors that Gronkowski’s retirement from professional football will be a short one are to be believed) was in town, along with his father, Gordy Gronkowski, and older brother Gordie Gronkowski, as part of The Center’s annual appeal and awards night. Shortly before 5 p.m., swarms of children filed into The Center’s half a gymnasium, the other half closed because of ongoing construction.

At 5:10, the DJ started the music, and the Gronkowskis swaggered in. Gronk briefly addressed the crowd. He wore a black David Pastrnak No. 88 Boston Bruins jersey, a nod from one Boston champion to another hoping to join him in the duck boat parade alumni association.

“We’re going to have some fun. We’re going to run some routes,” he said. “Most importantly, we’re going to Gronk spike.”

It was loud, but isn’t everything about Grokowski loud? The 6-foot-6 Gronkowski is a big man in perpetual motion. If Gronk wasn’t throwing a football, he was dancing. If he wasn’t dancing, he was clapping. We knew Gronkowski is a party in large human form, and nothing he did Wednesday suggested otherwise. He’s a fun magnet. Especially when he’s able to be a big kid surrounded by little ones.

A succession of children ran receiving routes, eager to catch a pass from Gronkowski. In the tight space of the gym, each route was pretty much the same, a basic 5-yard curl. Some of Gronk’s passes showed the kind of form that would make his former (future?) quarterback Tom Brady smile. Others were thrown sidearm. Each was thrown with eyes locked on the receiver. In his near-decade in the NFL, Gronkowski learned the receiver and quarterback must be on the same page.

Catches were met with a thumbs-up or a clap. Drops earned the same enthusiasm. A one-handed, over-the-shoulder catch earned an “Oh!” from Gronk and a nod. Game respects game.

And the high-fives. So many high-fives. If there’s something Gronk enjoys more than playing football or dancing, it’s giving high-fives. No upraised hand was not greeted in kind and with a smile.

That’s the big takeaway from the Gronkowski appearance. While brief, it was 100 percent, from not just Gronk but his father and brother, too. None of them looked as if they had someplace else to be. Each interacted with each child with gusto. From the smiles all the Gronkowskis wore from the second they arrived at the Alfond Youth and Community Center to when they said goodbye, it was obvious simply playing was a joy.

It ended with a display of Gronkowski’s famous touchdown celebration, the Gronk Spike. Four children were selected for a spike contest, but first, Gronk had to show how it’s done. He gripped a football in his right hand.

“You want the belly of the football to hit the ground,” Gronk said, and he demonstrated. The ball hit the hardwood floor with a boom that echoed, and bounced into the air as if pushed aloft by the eruption of cheers.

The four children each spiked, with the kids watching choosing a spiker named Bryce the winner of a chance to go against Gronk one-on-one. May the best spike win. Gronk went first, dancing first to ease into the moment. When it was Bryce’s turn, he did a quick shuffle of a dance move, then laid down a spike that drew another high-five from Gronk. When the crowd voted Bryce the winner, Gronk feigned outrage.

There was a group photo, the Gronkowskis in the middle of a sea of children. There was a selfie or two as Gronk made his way toward the door. Waves goodbye, applause.

Gronk had left the building.