Heracross did not originate from fanon, and the information on this page may not be entirely accurate to their canon. You may read more about this subject in the context of their canon on the following wiki(s):
Heracross is one of a handful of Pokémon capable of Mega Evolution. When equipped with a Heracronite, it can turn into Mega Heracross.
Heracross is a large bipedal, beetle-like Pokémon with a dark blue exoskeleton that is as hard as steel. On its forehead is a pronged horn, with a tip that differs per gender: Male Heracross have it roughly shaped like a cross while female Heracross have it in a heart shape. On either side of this horn is a short antenna found, each with a tip shaped like a sphere. Under these are yellow, oval eyes. Its thick forearms have a set of spikes on their side and its thighs have one spike each. It also has a single claw on each foot and two smaller ones on each arm. Heracross' back hals has some wing covers, which unfold when Heracross flies.
Heracross uses its horn to spoon under its enemies' belly to throw them far away. It is so powerful that it can throw things away that would be 100 times its own weight. Before it flings its foes away, it first digs its feet into the ground or under a tree's roots so it gets a firm footing so it doesn't tumble over. Heracross are usually found sipping honey, and are usually docile until disturbed. When interrupted while feeding itself, Heracross chases the intruders away with its horn.
Mega Heracross is a lot bulkier than regular Heracross. A part of its forehead has become completely orange. The antennae on its forehead are longer and have long, pointy tips. The color orange also rims its head, hands, shoulders and thighs. Its horn has turned into a large pincer, consisting of a massive, pronged horn on the top of its head, curving downwards, and a shorter pronged horn between its eyes, curving upwards. The shorter horn has one spike, and the bigger horn has two spikes, both pointing upwards and both placed on the direction the original horn pointed to. Its wing covers have turned bright yellow, and no longer open. Its forearms became extremely thick and spikeless. Its belly now contains blade-like openings not unlike the ones of an air conditioner. Since Mega Heracross now has a very high body temperature, these blade-like openings open sometimes, in order to let heat escape.
Minimum stats are calculated with 0 EVs, IVs of 0, and a hindering nature, if applicable.
Maximum stats are calculated with 252 EVs, IVs of 31, and a helpful nature, if applicable.
Heracross and Pinsir are the current counterparts to each other. Both are large Bug-type Pokémon that aren't known to evolve to or from any Pokémon, as well as being based on species used particularly in insect fighting. Both have a Mega Stone exclusive to one version or another, like how Pinsir and Heracross are exclusive to one version of a game. They also have the same height, and retain said height when Mega Evolving.
Heracross is based on the Japanese rhinoceros beetle, known for their amazing strength and popularly used in insect fighting, like Pinsir.
Mega Heracross is based on the Hercules beetle, which fits considering its name.