Roselyn Sanchez's appearances indicate the series order is incorrect. She is introduced as joining the RHD in #2 Dragnet: Coyote (2003), then disappears without explanation in the following show. She then reappears in #6 Dragnet: Abduction (2004), and again several shows later in #9 Dragnet: Riddance (2004). Each time she receives an "and" credit in the main credits. It's more likely the proper series order involved her appearances in the final three shows. This may also have been due to ABC canceling the series early and not broadcasting the final five shows.
Det. Frank Smith:
This city owes me a new pair of Italian ankle boots.
Det. Joe Friday: Yeah, Italian by way of Taiwan.
Beginning in season 2, Friday's voice overs at the beginning erroneously reference him and his partner. While this was correct in season 1 when both he and Frank Smith were detectives, in season 2, he is the lieutenant. As such, he was the unit supervisor and would not have a partner. He would supervise solo detectives or teams of detectives.
Jack Webb, creator of the series, does not receive screen credit.