PHILADELPHIA - Superstar Dwayne Johnson's latest performance wasn't part of a blockbuster movie but instead involved singing for one of his biggest (and oldest) fans.

On Wednesday, Jamie Klingler shared a video from the birthday surprise her grandmother will never forget. After hearing what a big fan "Grandmom Grover" was, "The Rock" himself recorded a birthday message that included a heartfelt thank you and a song. 

Her reaction is absolutely priceless.

Happy 100th birthday to Grandmom Grover, I cannot begin to thank @TheRock enough for making this happen. pic.twitter.com/qZ9iOcsiJI

— Jamie Klingler (@jamieklingler) October 2, 2019

Johnson has since replied to the Klingler's tweet saying, "stuff like this is always the best part of fame."