HeadOn - Apply directly to the forehead!
HeadOn is a fad based on a commercial about a so-claimed headache curing medicine called HeadOn. The commercial consisted of a woman repeatedly saying "HeadOn, apply directly to the forehead!" Despite, or perhaps because of how annoying the commercial of HeadOn was, it became an internet meme and later a fad on YTMND. The first person who made a HeadOn YTMND is unknown.
HeadOn is a product that was made by Miralus Healthcare at the time of the advertisements (and currently made by Sirvision, inc). It was meant to relieve headaches, a fact not mentioned in the commercial, probably because it doesn't actually relieve headaches: HeadOn uses homeopathy, which is no more effective than a placebo.
In 2006, HeadOn began advertising their product with a simple commercial: A woman, standing in front of a (depending on the version) blue or green grid background, applying the product directly to the forehead as a female voice repeats "HeadOn, apply directly to the forehead!" then saying it was available at pharmacies. That was the entire commercial.
Naturally, the internet began to make fun of it. One of these places was YTMND, which was no doubt attracted by the mindless repetition of one phrase over and over.