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During a virtual visit together, Fallon, 45, and Sandler, 53, tapped into their musical abilities to perform a song called "Don't Touch Grandma," reminding listeners to keep their distance from the elderly during the pandemic.
Both "Saturday Night Live" alums played guitars and performed their own vocals for the song.
"I love my grandma so much / I know she loves me, too," Fallon sang, followed by Sandler adding: "But thanks to this stupid virus / There are some new grandma rules."
In unison, they sang: "Don't touch grandma / leave her alone / you can spend a quarter to call her on the phone."
Fallon then sang about grandmothers' affinity for pinching cheeks, kissing heads and hugging.
"So don't touch grandma / Keep it to Zoom," the pair sang. "Or learn to play canasta from across the room."
Sandler then urged listeners to tell their grandma "no touchy, just looky."
Again, together: "Don't touch grandma / give her some space / even if your grandma wants to go to second base."
The pair then concluded the song by reminding fans that "you still can smell her grandma smell from 6 feet away."
Sandler recently performed a number dubbed "The Quarantine Song" on Fallon's online version of "The Tonight Show."
The song applauded health care workers for their unending dedication to fighting the coronavirus, even giving a shoutout to doctors in Italy, Spain and China, some of the countries facing the worst of the pandemic.