Read about the Young/Double Slit experiment. The whole reason why the Schrodingers Cat thought experiment and quantum mechanics came up in the first place was because they were able to cheat the observing condition, in other words they managed to "observe" something without that something knowing it was observed. It also demonstrates the concept of superposition, or having all the possibilities exist at the same time and even interfering and interacting with each other.

Really makes you think about what it exactly means for something to be observed and for all those possibilities to resolve themselves to one outcome. Or if we're the ones that simply branch off to another timeline that represents one of the outcomes.