Julianne Hough, Ashley Tisdale, Lindsay Lohan and Tobey Maguire were also spotted around L.A, while plenty of celebrity chefs cooked up treats in NYC and Chicago. Check out how these A-listers have been living large!
Happy sixth birthday, Harper and Gideon!
Neil Patrick Harris and his husband, David Burtka, took their twins to the Dominican Republic to celebrate their birthday, staying at Club Med Punta Cana.
WATCH: Neil Patrick Harris, Nick Lachey and More Super Adorable Celeb Kids Head Back-To-School
Isla Fisher and Mandy Moore also enjoyed some fun in the sun while mingling with guests at the Seventh Annual Veuve Clicquot Polo Classic at Will Rogers State Historic Park in Los Angeles on Oct. 15. Other guests included Kristen Bell, Matt Bomer, Lea Michele and Lauren Conrad.
Earlier that day, YouTube sensation Ricky Dillon, the voice of Aspen Heitz in the DreamWorks film, Trolls, hosted the General Mills Cereal Bedhead Dance Party at the P in Los Angeles.
"I love Cheerios, so when I learned General Mills Cereal wanted to partner with me in celebration of DreamWorks Trolls, I was thrilled to be involved," the 24-year-old singer told ET. "Plus, at the event there were troll hair glam stations! I already have troll-ish hair, so I was flattered to see everyone there inspired by my style."
Meanwhile, Allison Janney received a star on the Hollywood Walk of Fame on Oct. 15. The Mom star celebrated the big day with close friends, including her boyfriend, Philip Joncas, at L.A.'s Warwick nightclub, where the pair danced the night away while sipping on Casamigos Tequila cocktails.
Also celebrating a career milestone was Real Housewives of Beverly Hills star Mauricio Umansky, who was honored for his contribution to building a greater Los Angeles at the 2016 Builders Ball at The Beverly Wilshire Hotel in Beverly Hills, California, on Oct. 13.
Meanwhile, Tobey Maguire was spotted leaving West Hollywood hot spot, Delilah, on Oct. 14. The 41-year-old actor appeared to be "in good spirits," according to an eyewitness. Maguire and his wife, Jennifer Meyer, filed for divorce on Oct. 18 after nine years of marriage.
EXCLUSIVE: Inside Tobey Maguire and Jennifer Meyer’s Split
Also out and about was Ashley Tisdale and her husband, Christopher French, who attended NYLON's It Girl October Issue party, hosted by Tinashe, at the Doheny Room in West Hollywood, California, on Oct. 13.
Also in L.A., Julianne Hough showed off her abs while heading to a workout session on Oct. 18 with a FIJI Water bottle in hand.
Russell Wilson brightened up the hearts of a few young patients while stopping by at the Seattle Children's Hospital on Oct. 11. The Seattle Seahawks quarterback greeted families and posed for a few candid pictures, including one he posted to Instagram on Oct. 18. "Coen & Zion are twins that are fighters and Overcomers! Prayers are up! @SeattleChildrens," he wrote.
Congratulations are in order for Gordon Ramsay! The award-winning chef opened his fourth restaurant in Las Vegas, Gordon Ramsay Fish & Chips, located at The LINQ Promenade in Las Vegas.
And Norwegian DI Kygo had the chance to perform his hit, "Firestorm," with singer Conrad Sewell at 1 OAK LA on Oct. 15.
Over on the east coast, The Resolution Project hosted their 7th Annual Resolve Gala, where All-4-One took the stage for the ultimate #TBT performance at the Harvard Club in New York City on Oct. 13. The '90s hitmakers kicked off the evening with "I Can Love You Like That," followed by their hit song, "I Swear."
After performing at Sirius XM's private listening event, members of Kings of Leon were spotted having breakfast -- with beer! -- at CUT by Wolfgang Puck, located inside the new Four Seasons Downtown in NYC on Oct. 13.
Also in Manhattan, Daphne Oz celebrated the launch of Pure Leaf's new bagged and loose teas, sharing recipes from her cookbook, The Happy Cook, on Oct. 18.
EXCLUSIVE: Watch Rachael Ray Make Her Hilarious Acting Debut on 'Young & Hungry'!
Speaking of foodies, Giada De Laurentiis and Rachael Ray kicked off the 9th Annual New York City Wine and Food Festival on Oct. 15 at DI LUSSO, which showcased the best in Italian food.
Plus, chef Michael Symon cooked up some tasty treats with the help of One Tree Hill star Sophia Bush. The two shared cooking tips at Lipton's second Chef Fest dining event in Chicago on Oct. 15.
Taylor Spellman, host of Bravo's Yours, Mine or Ours, shared a candid behind-the-scenes snap of herself during production of the show earlier this week. Each episode follows Spellman and her co-host, Reza Farahan of Shahs of Sunset, as they work to overcome a people’s real estate roadblocks.
Designer Nikki Lund debuted her 2017 spring/summer collection during L.A. Style Fashion Week at the Pacific Design Center in West Hollywood on Oct. 14, celebrating the big day with close friend Joe Simpson.
Check out even more star sightings in the gallery below.
