Spur of the moment romance, now that is something we always want to hear about especially when it concerns pop diva Jennifer Lopez and her salsa musician husband Marc Anthony.

Jennifer Lopez and Marc Anthony secretly renewed their wedding vows in Las Vegas Sunday morning and this was a secret to them as well up to the last minute!

The couple, who have been married for little over four years, had gone to Las Vegas to enjoy the sights and excitements.

Saturday night, they went to clubs and delighted themselves with a show. In the early hours of Sunday morning, while still out on the town, out of the blue and on a completely spontaneous note, they decided they wanted to renew their vows. Next thing you know, they were on the phone searching for ministers.

Rev. Steven Smith officiated the ceremony at Caesars Palace’s Forum Tower Penthouse at 3:15 a.m. that same day, a hotel representative confirmed to People magazine.

As it happens, Lopez and Anthony were actually in town to celebrate the latter’s birthday – Anthony turned 40 on Sept. 16. What better way to make the anniversary special than to have your loved one promise everlasting love and promise it right back?

To make things even more interesting, they made it a double renewal, as they joined New York Mets outfielder Carlos Beltran and his wife Jessica.

Don’t feel sorry for Anthony having missed a birthday celebration last month though, as his wife actually organized a super-secret party for him which reportedly left the singer speechless.

She arranged a 1940s Cuban nightclub themed party at the Bowery Hotel in New York City, complete with salsa, mojitos, showgirls, and the exquisite Dita Von Teese performing one of her daring burlesque acts. The bash was followed by a vacation in Italy and Greece with their then 7-month-old twins.

Lopez and Anthony’s first exchange of marriage vows was just as surprising as their second, back in June 2004. In February of this year, they welcomed their first children together, twins Max and Emme. The twins are the first children for Lopez and the fourth and fifth for Anthony.

The couple has also taken its collaboration from the personal to the professional level. They recorded the duets “No Me Ames,” on Jennifer’s 1999 album “On the 6” and “Escapémonos” on Marc’s 2004 album “Amar Sin Mentiras,” among others.

They starred together in 2007’s “El Cantante,” a biopic about salsa legend Hector Lavoe, with Anthony in the title role and Lopez as Lavoe’s wife, Nilda. Also last year, they embarked on a joint tour that grabbed headlines due to Lopez’s interesting stage appearances – she was pregnant already and showing it but she only revealed the baby news during one of the couple’s last shows.