Press the flag Wait for the pony to disappear, and then continue with this: Press the up arrow to reveal something, and then down to hide. It works also if you scroll up or down over the project. Press the right arrow to reveal something else, and left to hide. Press 0 to reveal something else else, and 9 to hide. WOAH! Press 1 to reveal something else else else, and 2 to hide. Yie! Press the space bar to stop it, or the flag in order to reset and restart everything. And then when the flag is pressed again it works just fine :)
A big thanks to Bridget1476 for showing me Scratch and for helping me to learn how to do this!