The biggest problem to me, is that PJ is inventing rules on pixel art that are used nowhere else, then they get angry at anyone not knowing them by heart.
The word "NPA" is not a term used anywhere else, yet it's so common on PJ that people start using it here, where it makes no sense.
"JPG-ifying" is another non-existant term used when a lossy compression algorithm is used.
In terms of the weekly, there have been so many, that there are specific words and meanings you're supposed to know if you want to enter. In this context, "sprite" has a very specific PJ-weekly-only definition. I'm sure I could make an entry that makes half of the people think it's a sprite and the other half in doubt. Depending on the moderator you get, it would be randomly allowed or not into the contest, etc.
In terms of anywhere else in game design, a portrait is also a sprite. Some tiles are sprites, depending on the platform and programming. For a system like NES, "hardware sprite" is a precisely defined term and you only have 8 on one scanline. If you consider the whole world of game design and pixel art communities, the word "sprite" is very ambiguous though, but the PJ community acts like it's something very defined, based on arbitrary rules defined only by precedence (you only get the meaning if you've been a member for a while).
A study of the rules:
http://www.pixeljoint.com/pixelart/22521.htmDoes this image contain one or just two sprites? I'd say the PJ community would lean towards two. If the dog is closer to the person and they always move together, it would become very ambiguous.
The moderators would probably say: a sprite is just one "character". Now imagine a fighter that has two floating orbs as a weapon. The orbs rotate around the character and fire lasers. This would definately be only one "sprite". Let's say we change the orbs to two floating birds. Would this still count as one "sprite"? It probably would, tiny birds are probably not "characters" yet. Now where is the line between a girl and her dog being two sprites and a guy and two birds being only one?
The answer is: a moderator would decide it for you. The result is a heated discussion, just like the one we're witnessing in this thread.