These two kids decided to ruin a children's movie for their mom by cutting short the ending to Toy Story 3, letting Woody and the gang fall into a fiery pit and burn to death. Her reaction is just as good as you'd expect.
It's unclear exactly what makes mom such prime targets for pranks. Maybe it's because they tend to be extra gullible around their kids, or because they tend to be much nicer than those around them, but whatever it is, it works every time.
At least when they revealed what they'd done to her, she was able to laugh it off. But the thing with moms is you never know if they'll be holding onto this moment for years to come, ready to lash out at you about it at a moment's notice.
If you're planning a prank on your own mom, just be careful. They brought you into this world and they can take you out.