Think about it-I think everyone is in agreement that the point of the secret clock ending is for the crying child's spirit to help in organizing the happiest day, right? And the plush is the one who seems to be in charge of the operation.

Think about it-I think everyone is in agreement that the point of the secret clock ending is for the crying child's spirit to help in organizing the happiest day, right? And the plush is the one who seems to be in charge of the operation. The happiest day-designed to help William Afton's victims.

The plush is trying to undo the damage Will did. The plush is AGAINST Will.

If the plush was part of helping the dead spirits, then that immediately puts the idea of Will being the plush off the table.

In conclusion, despite the plush being in the private room, Will being the actual FNAF4 talking plush is just too out of character.