Serena Williams & Husband Cameo in Daughter's 'Nutcracker' Ballet Play

Serena Williams and her husband, Alexis Ohanian, are getting into the holiday spirit with a little local theater -- showing face in a ballet play ... one that their daughter is in too.

TMZ has obtained photos of the couple onstage Sunday during a production of "The Nutcracker" -- which was being put on by a ballet school near Palm Beach Gardens, FL ... where this play was going down at a local venue, with the little ones taking the lead.

Eyewitnesses tell us some adults made appearances as well ... including Serena and Alexis, whom we're told played guests at a party during one scene. They were definitely in character.

You can see Mama and Papa Bear dressed in full costumes as they acted out their parts -- this while the other kid actors/performers stood around and welcomed them onstage. It looks like a fancy pretend get-together, 'cause SW did a sweet little curtsy next to her hubby.

This Sunday matinee wasn't the only performance they did BTW -- we're told they did their thing for Saturday's show as well. Super cute obviously, and it just goes to show ... Serena and Alexis are very involved in their children's lives.

As you know ... Serena and Alexis got hitched in 2017 a couple months after they had their first daughter -- who's about 6 years old or so right now, and who was in this play.