Stars of Shortland Street tuned in to a surprise live on-set performance from the show's musical superfan, Jamie McDell, on Friday.
The Kiwi songbird - who has been following the TV soap for years -wrote a special birthday song to celebrate the series' 23rd year on air.
Cast members, including Michael Galvin, who plays Dr Chris Warner, were taken unaware when McDell rocked up with her guitar for a lunchtime singalong during filming.
"I was star-struck. I have loved the show since I was a little girl," McDell said. "I was asked to write a birthday tune as a surprise and everyone was really appreciative."
McDell dreamed up her own version of Happy Birthday. She included a line to reflect the high number of characters killed off down the years.