(l-r) Walker, Diaz, Giddens, and Celtics co-owner Wyc Grousbeck all donned green on Friday.

J.R. Giddens and Bill Walker received an unexpected helping hand on Friday while hosting a basketball clinic at the Young Achievers Pilot School in Mattapan.

Actress Cameron Diaz, who is in the area to film the upcoming “The Untitled Wichita Project,” stopped in to help build flower beds for the U.S. National Day of Service and Remembrance.

“We had a great day helping to improve the school through many projects,” Walker said. “I was very impressed with the dedication of employees from the Celtics, Harvard Pilgrim and City Year. Teaming up for this day of service has really made a difference in the school’s community.”

Diaz, Giddens, and Walker were joined by a team of 125 volunteers who helped complete projects at the school including a basketball court, outdoor classroom, and a picnic table area. Celtics Dance Team Director Marina Ortega also led a dance clinic. The day of service was organized by Boston Celtics, Harvard Pilgrim Health Care, City Year, and the Dartmouth Medical School Urban Scholars.

For a look back at the Celtics community service this summer, click here.