Like when the Grinch was surprised to hear singing instead of crying from the mountaintop in gift-less Whoville, an unfamiliar sound rose Sunday from the MetLife Stadium crowd.

After years of booing ownership, coaches and players on losing streaks, Giants fans turned the second half of Sunday’s game into a dance party, with the majority of the 77,399 in attendance staying until head coach Brian Daboll was soaked in Gatorade and a playoff spot was secured with a 38-10 win against the Colts.

“The energy was crazy,” safety Xavier McKinney said. “I’m glad they brought it. We needed it. I haven’t heard it that loud in a minute.”

Giants owner John Mara has noticed the temperature of the fan base shift.

“It just feels like I’m not as miserable as I have been the last few years,” Mara said. “And when I’m walking out to my car at the end of the night [fans aren’t] yelling, ‘You suck. Sell the team.’ For the time being anyway.”

All week the Giants pleaded with fans to shake off the New Year’s Eve partying and come out in droves for the first win-and-in game at home since 2011. Mother Nature offered a favor with 53-degree temperatures and light winds. Colts fans weren’t flooding the secondary market looking to buy tickets to see a doormat.

“You could feel the energy just driving here from the fans,” said Barkley, who co-signed a letter with other captains that was email-blasted to all season-ticket holders. “We challenged the fans — the coaches, the captains, the team — and they showed up. They were loud, made a lot of noise and created the energy that we needed, and we were able to win the game because of them.”

The Giants finished with a winning record at home (5-3-1) for the first time since 2016 — the last time they reached the playoffs. Locked in as the No. 6 seed in the NFC, they will not play another home game unless they advance to the NFC Championship against the No. 7 seed.

“The crowd was electric,” rookie Kayvon Thibodeaux said. “That is what we are going to need moving forward. Whatever home games we do get, however we can travel, fans, y’all need to be there.”

When defensive tackle Dexter Lawrence was reminded of the dark times and asked to compare those to Sunday, he quipped, “No boos!” Third-year left tackle Andrew Thomas called it “the most fans I’ve seen in the stands since I’ve been here.”

Instead, there were familiar chants of “Let’s Go Giants!” And a new one: “Dan-iel Jones!” which Saquon Barkley took as a sign that “he got the respect of the fans [because] not just anyone gets a chant in the stadium.” And a cheer when a sopping wet Daboll, courtesy of Jihad Ward and Julian Love, pumped his fist to the crowd to celebrate.

“He said, ‘Don’t go out there and f—ing around. I’m not playing. I know you,’ ” Ward said. “Then all of a sudden, me and Julian just poured Gatorade on … that bald-a– head.”