Good secret Prank?

[Wiseguy]

What are some good ways to pull pranks on my roommates without them knowing they were pranked? Example, two of them share a middle shower so I locked them both out so they would both blame it on the other

 

[LV1220]

Saran wrap over the toilet seat.
They put the seat up to pee and it goes everywhere.

Vaseline on the door handle.

Those aren't too secret though.

 

[TopPotts]

Remove the knob from one side of a door so that when the other knob is pulled, the whole thing comes out.
Sprinkle powdered sugar in one's bed.
Short sheet everyone's bed, including yours, but one. I did this to several Marines who were out one night. I made sure I went to bed at the same time they did so I could call out "they got mine, too". It was great. The culprits "had" to be the ones with okay beds.

 

[TopPotts]

Remove the knob from one side of a door so that when the other knob is pulled, the whole thing comes out.
Sprinkle powdered sugar in one's bed.
Short sheet everyone's bed, including yours, but one. I did this to several Marines who were out one night. I made sure I went to bed at the same time they did so I could call out "they got mine, too". It was great. The culprits "had" to be the ones with okay beds.