TCCLP
TCCLP is one of the most well-known (and longest) custom level sets, made by Tyler Sontag. As there was already a TylerS1.dat, Tyler changed the name to the abbreviation, which stands for Tyler's Chip's Challenge Level Pack. The set has been in production since May 8, 2004, and contains 350 levels, making it the third largest behind PB Gourami Levelsets and Jacques.
TCCLP has been notorious for having many unsolvable and plagiarized levels, but has also had many levels plagiarized from it and has inspired many levels. Three of its levels made it into CCLP3: Civilization of Creatures, All About Blocks, and Coal Mine.