A group of over 30 women, men and children performed the elaborate flash mob on Saturday at the Grove in Los Angeles. Van Dyke, who turned 90 on Sunday, enjoyed the show from above a nearby balcony.
The flash mob performed classic hits form the 1964 Disney classic such as "Chim Chim Cher-ee" and "Supercalifragilisticexpialidocious," as an ecstatic Van Dyke clapped and sang along.
At the tail-end of the flash mob, Van Dyke joined the group on the ground and together they performed a rousing rendition of "Let's Go Fly A Kite," while the flash mob members held up small kites that spelled out "Happy Birthday Dick."
Van Dyke tweeted about the flash mob, and said he was "grateful" that he can still have fun at his age.
"I am very grateful that at 90 years old, I can still go out and play," Van Dyke wrote.
Watch the flash mob performance below:
"Mary Poppins" was produced by Walt Disney Productions, a division of Disney, the parent company of ABC News.