William Shakespeare may be widely seen as the greatest writer of all time, but he can't seem to get a break from critics. Nearly 400 years after the Bard's death, two British academics have analyzed All's Well That Ends Well, and concluded that Shakespeare didn't write the play by himself. The assertion came as something of a surprise in literary circles, but it was far from the first claim to muddy Shakespeare's legacy. Here, a sampling of four controversies that have raised questions about Shakespeare and his work:

1. Did All's Well have a co-author?
Two Oxford University professors, Emma Smith and Laurie Maguire, looked long and hard at the language, rhyme, and style of All's Well That Ends Well, and determined that the 1606-1607 play bore the literary "fingerprint" of both Shakespeare and Thomas Middleton, who wrote The Changeling and Women Beware Women. All's Well contains spellings in line with Middleton's preferences, and a word — "ruttish," meaning lustful — that doesn't appear in Shakespeare's other writings, but can be found in Middleton's The Phoenix. Plenty of authors collaborated on plays at the time, and it looks like Shakespeare did, too, Maguire tells BBC News. "We need to think of it more as a film studio with teams of writers."

2. Was the Bard a pothead?
"Experts have long speculated whether drugs played a role in Shakespeare's genius," says Kai Ma at TIME. The theory seems to be supported by lines in his sonnets referring to a "noted weed" and "a journey in his head." And a South African anthropologist, Francis Thackeray, thinks the playwright definitely had an affinity for marijuana. In a 2001 study, Thackeray said he found cannabis residue (along with cocaine) on clay pipe fragments from Shakespeare's garden. The high-inducing plant was certainly available back in the Bard's time, as it was used to make textiles and rope.

3. Did he write more plays than we thought?
Plagiarism software is a godsend for college professors, says Boonsri Dickinson at Discovery, and not just because it can help them nab cheating students. In 2009, a University of London literature professor, Sir Brian Vickers, used a program called Pl@giarism to compare The Reign of Edward III, an unattributed play from the 1500s, to the works of Shakespeare. Vickers found more than 200 Shakespearean phrases — such as "come in person hither," "pale queene of night," and "thou art thy selfe," — in the mystery work, compared to just 20 shared word strings in the plays of other writers. With one exception, that is: There were also 200 shared phrases in the writing of Thomas Kyd, a Shakespeare contemporary, suggesting the two men co-wrote The Reign of Edward III.

4. Did Shakespeare write anything at all?
Thomas Middleton isn't the first writer to win posthumous credit for a Shakespeare play, says Sam Parker at The Huffington Post. The Bard's authorship has been questioned publicly since 1848, when Joseph C. Hart, in his book The Romance of Yachting, said that "Shakespeare merely adapted the works of more educated playwrights," making them popular by adding the occasional crude joke. Skeptics have suggested more than 70 different candidates, including Sir Walter Raleigh and dramatist Christopher Marlowe, as the real authors of Shakespeare's plays.