In addition to having access to videos of Supernatural or the television show of your choice, you will need to have some capturing software. This can be an image capturing app like Screen Capture for Google Chrome or you can use video capture software like Cam Studio 2.7. Either way, capture a series of consecutive still images or a brief video, using the DVD, BluRay or streamed video of Supernatural or the show you've chosen.
Next, use .gif creating software such as Jasc Animation shop (or an online .gif creator) to turn the still capture .jpgs or .avi video files into .gif files. You can also add text or a variety of effects.
The image here is a short clip of the television show Supernatural, with some simple light effects and the word “Supernatural” added in illustrate the process.