Classic rock joke

From the Dec Cluskey newsletter

The gags: [dating in 1957 - for those who remember and for those who don't remember. This humour is a shade of grey - but not what you may think at first.]

It's the summer of 1957 and Harold goes to pick up his date, Peggy
Sue.

Harold's a pretty hip guy with his own car and a duck tail hairdo.
When he goes to the front door, Peggy Sue's mother answers and invites
him in. "Peggy Sue's not ready yet, she says, "so why don't you have a
seat?"

Peggy Sue's mother asks Harold what they're planning to do.

Harold replies politely that they will probably just go to the
malt shop or to a drive-in movie.

Peggy Sue's mother responds, "Why don't you kids go out and screw?
I hear all the kids are doing it."

Naturally this comes as quite a surprise to Harold and he says
"Wha... Whaaat?"

"Yeah," says Peggy Sue's mother, "We know Peggy Sue really likes
to screw; why, she'd screw all night if we let her!"

Harold's eyes light up and he smiles from ear to ear. Immediately,
he has revised the plans for the evening. A few minutes later, Peggy
Sue comes downstairs in her little poodle skirt with her saddle shoes,
and announces that she's ready to go.

Almost breathless with anticipation, Harold escorts his date out
the front door while Mom is saying, "Have a good evening kids," with a
small wink for Harold.

About 20 minutes later, a thoroughly dishevelled Peggy Sue rushes
back into the house, slams the door behind her and screams at her
mother,

"Dammit, Mom! The Twist! The Twist! It's called The Twist!