Re: Terrible TOS performances....
Aurelan Kirk, Nancy Hedford, and Victor Lundin (the unamed Klingon Lt. from "Errand of Mercy") come to mind.
GARTH: Mister Spock, do you consider Captain Kirk and yourself brothers?
SPOCK: Captain Kirk speaks somewhat figuratively and with undue emotion. However, what he says is logical and I do, in fact, agree with it.