It's Armour Day at Under Armour's global headquarters in Locust Point, which means athletes, entertainers and other celebrities descending on South Baltimore.
The Baltimore brand is marking its 20th year making shirts, shoes, leggings and more and appears to have turned the annual event up a notch to celebrate.
"More celebrities, athletes, and artists at Armour Day than a red carpet event," tweeted one attendee from the event, apparently held at City Garage.
Skier Lindsey Vonn posted a video as she prepared for a karaoke competition with former NFL and MLB star Deion Sanders. Still waiting for the outcome of that.
Ripken Baseball tweeted that "Cal is with our friends at Under Armour today celebrating 20 incredible years!"
Gov. Larry Hogan posed for a photo with Sanders and Ray Lewis, who apparently introduced rapper Nelly. Boomer Esiason, Jordan Spieth, Roger Clemens and Tom Brady all made appearances.
"Watching Kevin Plank sing Sweet Caroline???," one tweet said.
Or was it Neil Diamond himself?
"#ArmourDay was great," tweeted comedian Gerry Dee, who also attended. "Neil Diamond, Kid Rock, Vanilla Ice, Nelly performed. Spieth, Brady, Vohn spoke. Thanks for including me @UnderArmour."
The company says the day is "dedicated to celebrating and honoring the contributions of our teammates and an opportunity to reflect on the past and look into the future."
So that means it's for employees only, as some, like Matt Owings, were sorry to learn.
"Whatever is happening at #ArmourDay I'm supremely jealous I'm not there," he tweeted.