Vaseline on Door-Knob

this prank is an oldie but a Goldie. Here is what you will need:

1: Vaseline/cream with a texture like Vaseline.
2: a door-knob that needs to be turned.

Step 1:
While your sis is sleeping, or when she is busy, sneak into her room and smother Vaseline all over the door-knob. (If she isn't in her room, then put Vaseline on the outside part of the door, this gives it a better effect, as she might notice the Vaseline and rub it off with a towel).
Step 2:
Wait..............

How the Prank Works:
The Vaseline slows the process of turning the door-knob, and what would usually take your sis 5 seconds to open the door-knob, it will take her about 5-10 mins!