A Fake beard is an item used in the Rocking Out quest. It is given to the player by Captain Braindeath in order to fool the bartender of The Rusty Anchor into purchasing some of Captain Braindeath's 'rum'. To do this the player dons the disguise, followed by several others, and poses as a number of customers seeking Braindeath's 'rum'. This fools the bartender into thinking that there is a high demand for the 'rum' and he will then sign an order for some.
After tricking the bartender, the fake beard, along with all other disguises, will automatically disappear. After the quest, players can get them back. Players who lose any of their disguises before tricking the bartender can get a free replacement from Captain Braindeath back on Braindeath Island.
You cannot equip nor unequip this item within The Rusty Anchor building. Trying to do so results in the "You should go outside and get changed there." message in the chatbox. This effect prevails even after you successfully trick the bartender and receive the order from him.