Adam Sandler Sings George Harrison Classic for Garry Shandling Memorial

Adam Sandler surprised some huge comedians with an emotional performance at Garry Shandling's memorial service.

Sandler hit the stage to sing George Harrison's "Give Me Love (Give Me Peace on Earth)" during Sunday's event in L.A. ... which was hosted by Judd Apatow.

We're told the memorial was equal parts somber and hysterical -- no surprise, considering who was in the room. What's a memorial service without a penis joke or two, right?

Some of the celebs there included Billy Crystal, Sarah Silverman, Linda Doucett, Conan O'Brien, Kevin Nealon, Ray Romano, Jon Favreau, Tim Allen, Vince Vaughn, Cheryl Hines and many more.

Shandling died in March of a massive heart attack.