My favorite wrong lyric moment occured at a farm - a bunch of us were all doing mundane chores in the seed room and singing the Beatles song "Michelle" - and during the line in French, Smokey Joe belts out

"Someday, monkeys won't play piano songs, play piano songs..."

we all froze, Joe sang a another line or 2 then realized the room had gone silent...."What? What?"

When we finished howling and explained, he petulantly pointed out that it wasn't any more senseless than "I am the Walrus, koo koo kachoo"