It happened during a seemingly innocent lake scene featuring two young cast members. The moment was meant to show them cooling off on a hot frontier day, but viewers who look closely — really closely — notice something completely out of place for the 1800s.

While the girls tread water and deliver their lines naturally, a modern object suddenly appears just beneath the surface. The camera pans for only a second, but long enough to catch what fans today immediately recognized: a bright, unmistakable flash of modern swimwear fabric, something that absolutely did not exist during the show’s historical time period.

In other words, while the characters were supposed to be skinny-dipping — as the storyline implied — the actresses were very clearly wearing protective bathing tops that became visible under the water. For 1970s viewers watching old televisions with low resolution, the mistake was invisible. But in today’s HD world, the blooper jumps out instantly.

Fans have reacted with a mixture of nostalgia and surprise. Many admit they watched the series for years without ever noticing the moment. Others say it makes them appreciate the cast even more — especially the child actors who had to film demanding outdoor water scenes while the crew worked hard to keep everything appropriate and comfortable.

It’s just one more reminder that even the most beloved classics carry secrets, bloopers, and behind-the-scenes stories we’re only discovering decades later.

And this one? Once you see it… you can’t unsee it.