When you see someone wearing a collar (particularly the ones made of leather - and we're not talking about the collar of a shirt), you can assume that they're under the control of someone else. It's also a popular device to use when brainwashing someone, and it may also be a part of a Go-Go Enslavement routine. If it's part of a person's normal costume, it's usually intended to suggest that [...] [tvtropes.org]