sprites

In computer graphics, a sprite is a two-dimensional image or animation that is integrated into a larger scene. Initially including just graphical objects handled separately from the memory bitmap of a video display, this now includes various manners of graphical overlays.
Originally, sprites were a method of integrating unrelated bitmaps so that they appeared to be part of the normal bitmap on a screen, such as creating an animated character that can be moved on a screen without altering the data defining the overall screen.
Z depth Sprites create an effective illusion when

• the image inside the sprite already depicts a three dimensional object;
• the animation is constantly changing or depicts rotation;
• the sprite exists only shortly;
• the depicted object has a similar appearance from many common viewing angles (such as something spherical);
• the perspective of the object from the viewer cannot possibly change fast enough for the viewer to discern a difference from true 3D geometry, as in the case of object a long distance away from the viewer in 3D space.
• the viewer accepts that the depicted object only has one perspective (such as small plants or leaves).

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