After affecting a zombie villager with a potion of weakness and using a golden apple on it, a second golden apple (if available in the same stack) will be consumed if the selected item in the hotbar does not change. However, there will be no food eating animation or sound effects--the golden apple count will just go down by one and the player will receive the effects of the golden apple.

To replicate this, have a zombie attack a villager and turn it into a zombie villager. Then, splash the zombie villager with a potion of weakness. Then, make sure to have a stack of at least two golden apples and use one on the zombie villager. Do not change the selected item in the hotbar, and a second apple will be used on the player.