Formula 407 - S1-E12
Revealing mistake: When Wonder Woman catches the first grenade and tosses it away, it falls 20 centimetres to the left of where the explosion takes place. If you watch carefully, you'll notice glittering sand where the explosion occurs, revealing where the powder was.
Formula 407 - S1-E12
Revealing mistake: During the fight in the lab, Trevor's stunt is noticeable.
Formula 407 - S1-E12
Revealing mistake: At the Ambassador's residence, when Wonder Woman jumps out of the balcony, the stunt trampoline's black canvas, bouncing upwards, is perfectly visible.
Formula 407 - S1-E12
Revealing mistake: On the beach, Wonder Woman's stunt is noticeable because of her shorter hair.
Revealing mistake: When Wonder Woman arrives at the Diamond H ranch, all further shots of the scenery outside seen from inside the house are of a blatant painted backdrop.
Answer: The first actress, Cloris Leachman appeared in the TV movie which ended up being the pilot for the series. At the time, Leachman was already starring in her own TV series "Phyllis" (a spin off her role in "The Mary Tyler Moore Show"). This was actually the 2nd TV movie meant to be a pilot and the first one wasn't picked up. It's likely she thought the show would be picked up. After season 1, in which Carolyn Jones played the role, ABC was slow to make a decision to pick up the series for season 2 and CBS picked up the series. When CBS picked up the series, they changed the time setting of the show and replaced all the actors, with the exception of Carter and Waggoner (with Waggoner playing a different role technically), resulting in Beatrice Straight being cast.
Bishop73