Pennetta, at 33 the oldest first-time Grand Slam finalist in the Open era, on Saturday became the first Italian to win the US Open women's crown with an efficient 7-6 (4), 6-2 victory over compatriot and childhood friend Roberta Vinci.
Third seed Stan Wawrinka rose to the occasion once again to beat top-seeded defending champion Novak Djokovic 6-7(1) 6-4 7-5 6-3 and win the US Open on Sunday for the third grand slam title of his career.
Highlights of day four of the 2016 US Open tournament
Kei Nishikori battled for the second match in succession before claiming his place in the third round of the US Open on Thursday.
World number one Novak Djokovic received a free pass into the third round of the US Open when Jiri Vesely of the Czech Republic withdrew from their match on Wednesday due to a left forearm injury.
2nd round match at 2016 US Open
Highlights of day two of the 2016 US Open tournament
Highlights of day one of the 2016 US Open tournament
Roberta Vinci shrugged off her US Open final loss to fellow Italian Flavia Pennetta by dreaming of home-made pasta and enjoying her last New York hamburger.
When Wawrinka served the first ball, empty seats were few and far between. By the time he closed out the 6-4, 6-4, 6-0 win, the stadium was less than a third full. Everyone had rushed to see the end of Roger Federer's sprint past No. 12 Richard Gasquet.
Serena Williams kept her bid for a calendar-year grand slam on track, powering past big sister Venus 6-2 1-6 6-3 on a steamy star-studded night at the US Open on Tuesday.
Andy Murray watched a 130 mph ace zoom by to create a two-set deficit at the US Open, and then sat in his changeover chair and cursed at himself, over and over and over.
Roger Federer produced another bright effort while Britain's Johanna Konta continued to enjoy her time in the sun and the US Open spotlight on Saturday reaching the fourth round of a grand slam for the first time.