Why does Barney dramatically cut the phone cord when it rings? He could just unplug the cord from either the wall or the phone. Or were phones in that era hard-wired at both ends?
Often, yes. Sometimes they had 4-pronged plugs that went into wall jacks, but often they were permanently wired in. The modern modular connector wasn't introduced until the mid-1970s.
On the Laugh-In "If X married Y" jokes, I remember an issue of Games Magazine that had a puzzle game based on that theme. I think it gave descriptions rather than the actual names, and you had to guess the names and the punch line. The one I remember was a double, with an extra pun on top: If Diana Prince married the builder of the Spruce Goose, divorced him, and got remarried to Nixon's Secretary of State, she'd be
Wonder Hughes Kissinger now.