In order to understand Inglip, one must understand or have had some experience with the internet Captcha
system. A "captcha" is a program that forces you to type in the text it shows in order to proceed, for the purpose of verifying that you are not indeed a computer bot. The words are often difficult to read and even more often are not actual words.
A lot of humor is derived from the two words which get randomly chosen for you to type. Sometimes they create a weird phrase, and other times they are just funny since they have nothing to do with one another. Artwork has been drawn, comic strips have been made, T-Shirts produced, all over the accidental humor that captchas provide.
And so we have Inglip, which started as a black and white sketch drawing utilizing words from a captcha, one of which was the nonsensical "Inglip". The phrase in its entirety was "Inglip Summoned", and the four panel cartoon posted by a Reddit user ended with that phrase over the haunting sketch of a face.
Since then, the Inglip meme has expanded, and the idea that an internet captcha would be used to summon anything provided fertile ground for humorous takes on the concept.
Now, not only has Reddit created a category named the "Inglipnomicon compendium", but there is even a Wiki project in the works to catalog all the uses of Inglip and its subsequent summonings.
The face of Inglip himself has transformed and has now been usurped to become referred to as "OMG Rage Face