Recycled Movie Costumes is a website that tracks costumes which appear in different films and TV shows.
The site is based on the fact that costumes often appear in different productions, as it is too expensive to create new ones for individual projects.
This means that because films and TV shows rent items from a costume house, the chances are that they have been seen somewhere on screen before.
Although they can be altered, costumes can often appear almost exactly as they did before.
For example, there is a purple top that has been spotted in an episode of Firefly (2002) and Eternal Sunshine of the Spotless Mind (2004).
There are many other examples on the site, neatly arranged by historical era, which is a good example of crowdsourcing information from users.