...for there is an upstart Crow, beautified with our feathers, that with his Tygers hart wrapt in a Players hyde, supposes he is as well able to bombast out a blanke verse as the best of you: and being an absolute Johannes fac totum, is in his owne conceit the onely Shake-scene in a countrey ...

Robert Greene (11 July 1558 – 3 September 1592) was an English author best known for a posthumous pamphlet attributed to him, Greene's Groats-Worth of Wit, widely believed to contain a polemic attack onWilliam Shakespeare.  In it, Greene disparages Shakespeare, for being an actor who has the temerity to write plays, and for committing plagiarism. The passage quotes a line which is purportedly from Shakespeare's playHenry VI, part 3, but scholars are not agreed on exactly what is meant by this cryptic allusion. Some scholars think that all or part of the Groats-Worth may have been written shortly after Greene's death by one of his fellow writers (the pamphlet's printer, Henry Chettle, being the favoured candidate) hoping to capitalize on a lurid tale of death-bed repentance. Hanspeter Born, argues that Greene wrote the whole of Groats-Worth and that his deathbed attack on the „upstart Crow“ was provoked by Shakespeare’s interference with Greene’s play A Knack to Know a Knave.^[4] Why Greene was Angry at Shakespeare.

Greene's colourful and irresponsible character have led some, including Stephen Greenblatt, to speculate that Greene may have served as the model for Shakespeare's Falstaff.

More on him here