While watching The Menagerie, I couldn't help but notice that Number One's (Majel Barrett's) voice sounded very familiar. I eventually realized that it had to be the voice of the ship's computer in Star Trek TNG. At one point in the episode, where she is a possible mate, another character comments that "They'd have more luck crossing him with a computer." I got a big laugh out of this, as it's essentially a prescient joke about Star Trek TNG, which wouldn't be made until over two decades later.