Visual Effects from GoF
The company, BUF, is one of many that worked on some of the special effects for Harry Potter and The Goblet of Fire; has recently released 18 new pictures showing how they did a few scenes in the movie GoF. The effects shown, was the fireplace scene with the image of Sirius, and Moody during his transformation back into Crouch.
They're definitely worth checking out, and in just in case, they also have some other movies in there as well, if you hit the back button (such as Batman Beyond).
**This thanks to HPANA