Epic Face (also known as Awesome Face) is the name given to a round yellow-colored face, with eyes looking upward to it's left and a big smiling mouth, so as to give the impression of a blissfully happy, joyful face.
Due to its simplistic nature, the face has been manipulated and exploited greatly. It is regularly seen in popular web forums (such as SomethingAwful) as well as image boards (such as 4chan), and even occasionally in children's websites (such as Roblox), in both unaltered and altered forms. It is commonly used as a reaction face “To express a high level of approval or ironically to express disdain".
According to gaming blog driph (administrated by Chris Ainsworth), the Awesome Face was part of a series of emoticons designed and illustrated for the Pokemon-related web forum Pokemopolis. According to the designer (whose identity is unknown), the face is best described as a “ridiculous childish glee”. It's design might be a reference to certain Pokemon such as Lavender Town GHOST and Missingno's GHOST form.
Awesome Face later gained popularity through popular forums and image boards, notably SomethingAwful and 4January 2007, a forum thread on SomethingAwful, started by user Kiss My Butt America, outlined the large popularity among the forums’ users and the variations caused due to its popularity. Due to the prolific nature of the Awesome Face, it can be considered to be an “established” or “classic” meme, as mentioned by OhInternet.