The term "relative unknown" refers to people, usually actors or other celebrities, who may have a cult following or be somewhat famous (especially perhaps in only a certain area) but are not expected to draw in crowds on their name power alone. For example, in about 2009 Emily Blunt was a big name in the UK but a nobody in the US, so her film Gulliver's Travels (2010) opened to poor reception in the latter country.
The idea is demonstrated in a few tropes, please correct any link that send you here to point to the correct one:
- C-List Fodder: When a major attack happens, it will be the relative unknown characters that are killed, so that they are established and kind-of famous, but not the main ones.
- Darkhorse Casting: Deliberately looking for relative unknown actors for a movie cast, or basically having the opposite of an All-Star Cast.