Who said "Do unto others as you'd have them do unto you"?

This quote is attributed to Kenny McCormick.

Do unto others as you'd have them do unto you - Kenny McCormick

"Do unto others as you'd have them do unto you"

Kenny McCormick Kindness

"Mmph mmph mrmph!"

"I'm not fat, I'm just big boned"

"Dude, we're in third grade"

"This is so cool"

"A good man treats his wife with respect."

"Kindness always comes back around."

"The power of a smile can change everything."

"Kindness is weakness to some. Not to me."