Fans of the music star replied to the post, saying it was "awesome" and "better than the original".
Since Pharrell tweeted the link overnight on Wednesday NZT, stories of the retirees antics have been splashed across global news websites, including the Huffington Post, Daily Mail, People Magazine, ITV News, Celebuzz, and Mashable, with glowing reviews.
Watch: 'Happy' pensioners in Pharrell parody
"When you see these seniors boogieing down, you'll want to get right up and dance along," the Huffington Post said, calling the video "simply irresistible".
The video for 80-Odd Years of Happy was posted on YouTube on July 19, with the caption saying the residents wanted to "show their children and grandchildren just what they're made of".
They had "combined all their considerable talents to come up with this tribute", in which they mimic the moves and scenes created by Pharrell in the original.
"It's just about celebrating the fact that just because you might have only a few years under your belt, it doesn't matter, you can still do these things," David King, a spokesperson for Ryman Health Care, told Daily Mail Australia.
The star of the video is 79-year-old Alister Leckie, a former engineer who dons a white shirt, bow-tie and Pharrell-like buffalo hat to play the part.
He had "never done anything like that before, and absolutely loved it", Mr King said.
The pensioners are reportedly discussing a sequel.
Happy, which featured on the soundtrack for Despicable Me 2, soared to the top of the charts in more than 20 countries, including New Zealand. It is the lead single from Pharrell's latest album, Girl, and was nominated for a Best Original Song Oscar at the 86th Academy Awards in March.
The video spawned hundreds of cover versions from various countries around the world, with people dancing through the streets to the song.
