A mondegreen is the mishearing (usually accidental) of a phrase as a homophone or near-homophone in such a way that it acquires a new (funny) meaning.

“Almost Cut My Hair”
David Crosby
“Like looking into a mirror and seeing a Polish car”
Real Lyrics: Like looking into a mirror and seeing a police car

“Chicago”
Graham Nash
“And they’ve changed him into a chair”
Real Lyrics: And they’ve chained him to a chair

“Cowgirl In The Sand”
Neil Young
“Hello movie in the dark”
Real Lyrics: Hello ruby in the dust

“Don’t Let It Bring You Down”
Neil Young
“Can you hear the silent moon?”
Real Lyrics: Can you hear the sirens moan?

“Faith In Me”
Stephen Stills
“Masturbate with me”
Real Lyrics: Have some faith in me

“Helpless”
Neil Young
“Sweet comfort memory despair”
Real Lyrics: With dream comfort memory to spare

“Helplessly Hoping”
Stephen Stills
“Her hard-lickin’ lover’s nearby”
Real Lyrics: Her harlequin hovers nearby

“Ohio”
Neil Young
“Four dead in Ohio – Five!”
Real Lyrics: Four dead in Ohio – Why?

“Old Man”
Neil Young
“Old man look at my wife, I am in love like you were”
Real Lyrics: Old man look at my life, I am a lot like you were

“Marrakesh Express “
Graham Nash
“Don’t you know we’re writing American Express”
Real Lyrics: Don’t you know we’re riding on the Marrakesh Express

“Southern Cross”
Stephen Stills
“I have been all around the world, looking for that Mormon girl”
Real Lyrics: I have been all around the world, looking for that woman/girl

“Suite: Judy Blue Eyes”
Stephen Stills
“Ruby, throw dead sparrow”
Real Lyrics: Ruby throated sparrow

“Teach Your Children”
Graham Nash
“Can’t know the fears, that you ever screw by”
Real Lyrics: Can’t know the fears, that your elders grew by

“You who are on the road must have a coat”
Real Lyrics: You who are on the road must have a code

“The one-day bitch”
Real Lyrics: The one they pick’s