Triplets Use Yearbook Photos as Clever Opportunity for ‘Knock Knock’ Joke

— -- Knock knock. Who’s there? Three clever triplets who are definitely finishing up their senior year in style.

Kassidy, Keaton and Kylee Durham, of Fort Wort, Texas, knew the best way to grab attention in their final high school yearbook ahead of graduation.

Instead of using the allotted space for a senior quote, they instead chose to coordinate a funny “knock knock” joke. "Knock knock," read the quote under Kassidy. "Who's there?" read the one under Keaton. "Not the triplets. We graduated," read Kylee's quote.

“My parents thought it was a cute idea. They said it was ‘brilliant,’” Kassidy wrote to ABC News.

The siblings didn’t necessarily keep it a surprise from their fellow peers, but were surprised themselves by the attention the joke is getting.

“I think it was more of a surprise to us from how many people mentioned it on Twitter and how fast it blew up,” she said.

Their last day at Northwest High School is June 7 before they each head off to the University of North Texas in the fall.