The phrase "fake beard" refers to a false or artificial beard that someone wears, usually to disguise themselves or hide their true identity. Full definition
One year, my (then) baby cousin was sitting in his lap and pulled his white fake beard and started crying. (thechrisellefactor.com)
And when one of the characters ate salmon through a dirty fake beard, we ate cold noodles, covered in charcoal powder, with lumps of salmon in. (30datesblog.com)
When McGill and his friends don fake beards for a command performance of «Man of Constant Sorrow,» the hit single they recorded (as the Soggy Bottom Boys), the song transcends jokiness or kitsch. (nytimes.com)