When someone is sleeping change their clock time and wake them up late for school/work.
If you have the type of light switches where you can change how bright they are, make them darker as slow as you can while people are in the room and see if they notice. XD
At a clothes store(where there is a lot of people) start talking to the mannequin like it's your mom then when they look away change it with a person that looks like the mannequin and when they say that the mannequin is not alive have the mannequin say don't talk to my child like that(see ho
Get your friends phone and change all their contacts names to Star Wars/ Something Funny.
The next time a friend leaves their phone with you, take a ton of selfies and change their wallpaper to the best one.
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