Flipper and the Bounty - S2-E13
Visible crew/equipment: After Bud wakes up all alone in Bligh's cabin, he soon realises all the doors are locked. Then, just as Bud rushes over to the stern window (particularly the second time), a seated crew member is visible at the bottom right corner of the screen; we can see the movement of a leg and two hands (so, it's not a mannequin).
The Alexander the Greater Affair (1) - S2-E1
Character mistake: When Alexander organizes the human chess game in his courtyard, the "pieces" stand the wrong way on the board, with a dark square in the lower right hand corner. That corner is always a light square. (00:22:50)
Other mistake: One of the natives putting the captured Seaview personnel into the cave is wearing laced up sneakers. (00:36:25)