One of the bassist I play with counts in one of our songs. It starts on the 3rd note of the bassline, so he counts us in, but he doesn't get that "the one" is on his third note, so he counts 1, 2, 3, 4 and then plays 1, 2, and we all come in on the following 3 which is actually a 1. It's pretty embarassing on stage as people can hear him count it in