WATCH: Jesse Tyler Ferguson Receives B-Day Surprise from Gay Boston Choir

On Monday, Jesse Tyler Ferguson celebrated an unexpectedly musical birthday during a speaking engagement at Boston's Wilbur Theatre. Modern Family costar Eric Stonestreet, who plays his partner, Cam, on the show, surprised Ferguson onstage by unveiling the Boston Gay Men's Chorus.

After singing "Happy Birthday," the 85-member ensemble gave a choreographed performance of Katy Perry's "Firework." Fans laughed and cheered as the astonished Ferguson, who had just turned 47, grabbed a colorful streamer and joined the production.

"I have never been so surprised in my entire life," said Ferguson after the sparkling performance. "You sound unbelievable."