If one of the people questioned during the investigation of a Monster of the Week is a policeman or a marine or a scientist or some other person who was on the job when they saw the thing or event, there's a good bet they'll say some variation on this line: "I've been a biologist for thirty-four years, and I've never seen anything like this before", "You see some strange things on this job, but I've never seen anything like this before", etc; much of the time the line is spoken in such a way as to suggest that the speaker will be haunted and traumatized by what they saw to the end of their days. The message is clear: if it's got the professionals spooked, you must be onto something.