That show Are You Smarter Than a Fifth Grader must be pretty hard — ten-year-olds these days are smarter than the greatest repository of national knowledge, the Smithsonian.
Kenton Stufflebeam (what a great name!) was perusing the Tower of Time exhibit in the Natural History museum and noticed that the display tagged "Precambrian" as an era. It's not! Kenton let them know. According to the museum, Kenton was "spot on," adding, "The Precambrian is a dimensionless unit of time, which embraces all the time between the origin of Earth and the beginning of the Cambrian Period of geologic time." They made the big fixeroo by painting over the word "era."
Kenton said he was glad to get the letter from the museum congratulating him on his find, but he wishes they'd spelled his name right. (I cannot make this up.) Maybe Kenton has a job waiting for him when he grows up.