I was going to start a new thread, but since the PW+ Alphabetics board was discussed, I guess it's relevant to the topic...
How about set changes (minor or major) made to a set or prop shortly after making its debut on TV...
TPIR
The Bonus Game windows were yellow for the first week, then blue the following week.
The turntable added lights and extra stripes only after 6 or 7 shows (I forget how many exactly, someone posted it)
The bucket in Push Over was changed from red to yellow once it was discovered it blended in with the red on the turntable at the time.
The lights in Cover Up were changed from red to blue
The lights in It's In the Bag were changed from yellow to blue
First playing or so of Clearance Sale, the tags were white with red numbers, then changed to red with white numbers.
An eggcrate display was added to Time is Money to indicate how many the contestant got WRONG (why they didn't tell the player how many they got RIGHT, I dunno, one of the many reasons the game was axed)