"If you can't draw, never fear, just steal some graphics from your favorite video game. And add yet another unlicensed pixel comic to the overcrowded, over stunk landfill of web comics." - Strong Bad
The first sprite comic was Neglected Mario Characters. However, Bob and George (a parody of the Mega Man series) popularized these comics. Sprite comics were the most popular in 2000-2007. However, they dropped in popularity recently.
Sprite comics have some recurring problems. Due to the ease of making them, untalented writer will make comics and not put effort into it. Not thinking about the color palette can easily ruin a sprite comic. While these sprite comics are easy to make, they still have to edited, but people tend to forget this. There are potential legal problems although these problems almost never comes up and the video game companies usually just ignore them.