Robert Pattinson and Kristen Stewart were among the most-ogled guests at the Saturday wedding of pals Kevin Turen (a Hollywood producer) and Evelina Oboza in Englewood, NJ -- a bash also attended by such Hollywood A-listers as Andrew Garfield, Zac Efron and Drew Barrymore's new husband Will Kopelman, plus New Jersey Senator Frank Lautenberg.
"Rob and Kristen were all over each other," a wedding guest tells Us Weekly, adding that Kopelman, Efron, musician Matt White and Harry Morton were the groomsmen at the wild bash.
Fellow Brits Pattinson, 26 and Garfield, 28, found a unique way to bond with Efron, 24: "There was a little area where you could go and play music," the guest explains. "Rob sang, Andrew played the bongos, Zac played the guitar. It was a whole spectacle!"
Earlier in the night, the A-list hunks helped groom Turen during the traditional Jewish hora dance, lifting him on his chair as the crowd cheered. For his part, Efron "was rapping towards the end of the wedding. It was hysterical!" the guest raves.
Revelers partied until the wee hours -- 7 a.m.! -- and, the next day, 22-year-old Stewart joined her beau plus Garfield (whose girlfriend Emma Stone had a work commitment) and Efron at the pool on the grounds of the home. (Also going stag for the wedding with just-married Kopelman, whose pregnant wife Barrymore was a no-show.)