How to build spider prank with remote - Remote Control
First, the remote has it's power, then add a slide dimmer (controls the spider), then add a wireless transmitter on channel B. All of these are on a board.
Use another board to add the following. First, power. Second, Wireless Receiver on Channel B, and then servo. Place spider on top of Servo arm with a rubber band or something to attach spider.
Control the Spider with the Remote
Because the remote works with the receiver, the spider can move when you aren't around.. Which makes it easy to prank anyone with a huge spider or whatever you want on the arm. Slide the dimmer to control the spider.