Alec Mazo and Edyta Sliwinska's bachelor and bachelorette parties could have doubled as a Dancing with the Stars' reunion.

The Dancing with the Stars' professional two-steppers partied over the weekend in Las Vegas to celebrate their upcoming nuptials, People reported Monday.  They were joined by Kelly Monaco -- who took home Season 1's mirror ball trophy with Mazo -- as well as two-time show champ Cheryl Burke and her boyfriend Matthew Lawrence; and fellow professional dancers Kym Johnson and Karina Smirnoff.

With Mazo and Sliwinska's wedding less than a month away, the two arrived in Sin City with their guests on Saturday and got situated in their suites at the Planet Hollywood Hotel before splitting into groups for the separate bachelor and bachelorette parties, People reported.  While the girls had drinks at Heart Bar and -- not surprisingly -- danced the night away at the Palms' Moon Nightclub, the guys had fun on a party boat at nearby Lake Mead.

The festivities ended on Sunday, according to People, when the groups reconvened and relaxed at Bare -- a top-optional pool at Mirage -- before trying their luck at a casino.

Mazo and Sliwinska were professional partners prior to appearing on Dancing with the Stars' first season. 

Sliwinska is the only professional dancer to appear in all four installments of Dancing with the Stars, as she was paired with Evander Holyfield in Season 1; George Hamilton in Season 2; Joseph Lawrence in Season 3; and John Ratzenberger in Season 4.  After Mazo won the mirror ball trophy with Monaco in Season 1, he didn't participate in the show's next two editions before returning for the fourth installment and being paired with Paulina Porizkova.  They were the first couple eliminated.

Mazo and Sliwinska became engaged last fall and are planning to wed in September.