Factual error: Though this episode is set in then-present-day 1961, the fistful of prop money the bartender is holding is not contemporary. It appears to be copies of 1880s U.S. Currency, though it's been reproduced as smaller, 20th Century sized bills rather than the larger ones that were standard in the 1800s. All in all, not something his bar patrons would likely be paying the bartender with in the 1960s.
Revealing mistake: Mr. & Mrs. Castle wish for a million dollars in 5 and 10 dollar bills. But the bills they receive all have the same pattern printed on both sides, a pattern which which doesn't resemble any real US currency. There's also not nearly enough of the bills to total a million dollars.
Continuity mistake: The flying saucer the old woman hacks to pieces with an axe is noticeably not the same one that lands in her attic in the beginning. A cruder version was built for the axing scene because the model used was a studio keepsake - the original spaceship from the classic sf film "Forbidden Planet."