LAS VEGAS – Publishing icon and Viagra fancier Hugh Hefner celebrated his 83rd birthday in Las Vegas Saturday with a full-slate of parties that included mega photo opps with girlfriends past and present, including his current threesome of Crystal Harris, 22, and 19-year-old twin sisters Karissa and Kristina Shannon, and original “Girls Next Door” Holly Madison, Bridget Marquardt and Kendra Wilkinson.

Most of the day was spent at the Palms Resort and Casino. Activities included a midday pool session, after which Hef and entourage prepared for the evening’s festivities of dinner at N9NE restaurant followed by a private party at the Playboy Club and Moon.

Hef’s birthday is April 9, but that falls on a weekday and great celebrations are made for weekends. Despite trouble with the economy and at the company he founded in 1953 — which became universally synonymous with affluence and sex — Hefner refuses to surrender to either the times or his age.

Apparently, the day’s festivities went off without a hitch, except for one instance of tepid poolside catiness between former No. 1 girlfriend Holly Madison and local entertainment reporter Alicia Jacobs caught by the eagle eyes of Norm Clarke in his Vegas Confidential column.

Daily Babylon sends a hale and hearty Happy Birthday to the king of classy sex, Hugh Hefner.

Check out some more photos of the special day on GossipGirl.com.