Only people who watch Doctor Who and know the Weeping Angels will get that joke.
The Weeping Angels are aliens that are statues as long as you look at them. But they are so fast, even if you just blink, they will get you. They prey on humans by sending them back in time to live to death and feeding on the time travel engergy.
Doctor Who belongs to BBC
That angel belongs to the person who owned this flat before me and she didn't took it with her :C