They danced just steps from the bride and groom and even posed for photographs.
One problem: They weren't invited to the wedding.
The bride and groom, Karen Fox and Michael Tufo, only found out that their wedding at the Rock Island Lake Club in Sparta had been crashed when they opened presents the next day.
They found a card containing a Polaroid photo of the couple along with a "buck for luck" and a note that read: "Congratulations! Sorry for crashing your wedding. Best of luck."
The bride posted an image of the card to Facebook.
"I'd like to thank everyone who shared our special day with us... especially these 2! Well played my friends... well played!!!" she wrote.
Now the wedding party wants to find out the identities of the mystery crashers. There were no other events at the venue that day, so they couldn't have stumbled in by accident.
Their wedding planner, Heather Truesdale, told Inside Edition she suspects the couple arrived later in the evening, saw two guests hadn't arrived and took their seats.
Wedding photographer Joseph Costa of La Moda Studio took multiple photos of the couple enjoying the evening.
"I didn't see them really talking to anybody," he told Inside Edition. "It didn't seem like they knew anyone, but they were having such a good time."
The newlyweds don't appear to mind.
"We laughed," the bride told WCBS from their honeymoon. "We were like, 'Oh my God, we got wedding crashed! That's funny.'"