Face but no head
A stupid person who acts like they have a brain but they don’t. They’re like a face with no head and no idea what’s going on.
"She’s face but no head, like she’s a brainless mannequin with a face.", @mannequinhead
"He’s face but no head, like a dummy with a face who thinks he’s smart.", @dummyhead2021
"That guy is face but no head, like he’s a stupid statue with a face.", @statedeadhead"