100,000 BC - S1-E1
Continuity mistake: When Ian and Barbara enter the TARDIS for the first time, Susan operates the door switch. Later on, when the Doctor electrocutes Ian, he uses the exact same switch.
Continuity mistake: The date of Helen Kimble's murder is given here as Sept. 19, 1961. Previous episodes, however, had established it as occurring on Sept. 17, 1960.
Continuity mistake: When the lab equipment shorts out after the earthquake, the unconscious Major Brothers is lying with his head propped up against the wall. But when Hamilton reaches him in the next shot, he's suddenly lying flat and is nowhere near the wall. (00:21:45)
Continuity mistake: During the 12/29/04 episode, Emily goes to look for Conner. Emily goes to a carpentry shop and asks the owner if he has seen Conner. She tells the owner that Conner "just moved here from Canada." Acually, she's looking for him in Canada. In the next scene, the show gets it right, and the owner asks Conner "Is that why you left the States?"
Oh, My Aching Antenna - S1-E33
Continuity mistake: Even though Tim and Uncle Martin live on the 2nd floor at Mrs. Brown's above the garage, every view outside the living room window with the sheer drapes shows the house across the street from a ground floor perspective. This happens in multiple episodes.
Continuity mistake: When Burke's partners arrive to question Mimsy Grove, she's facing away from them, bending over to untangle her boat's mooring line. But in the very next shot, she's immediately standing up straight and has turned around to face them. (00:38:15)
The Cousins - S1-E37
Continuity mistake: When Mr. Castle complains that Martin Lane is a traitor, his secretary reminds him that he himself has declared Martin to be "the best managing editor in the country." Mr. Castle then takes a seat while holding his newspaper, but in the next shot his hands are empty as he impatiently stands up.
Spur Line to Shady Rest - S1-E1
Continuity mistake: When the Cannonball is preparing to leave, Uncle Joe has his hat. When the scene cuts to him helping Kate onto the Passenger Car, his hat is suddenly missing and nowhere to be seen.