Pharrell filed a lawsuit against Will.i.am in order to stop Will.i.am from preventing him to use his "i am OTHER" brand.
Will.i.am and Pharrell have been beefing legally over Pharrell's i am OTHER brand being too similar to Will's copyrighted "I AM" phrase. There was a misunderstanding at first that Will was actually suing Pharrell over the matter, when he had just filed a notice of opposition-- but now someone is indeed suing, and it's not Will.i.am, it's Pharrell.
TMZ reports that Pharrell went ahead and filed a lawsuit against Will in federal court in New York, in an effort to impede Will from stopping him. Pharrell claims that the two artists are using the "I AM" phrase in completely different ways. Pharrell cites that Will is using it a Seussian way (yes, he's referencing Dr. Seuss). As explained in the suit, Will is using "I AM" to play off his own name (he then goes on to quote Dr. Seuss, "Sam I Am.").
Pharrell, on the other hand, says,"In contrast, the I Am Other mark means 'I am something else,' leaving what that 'else' is to the imagination of the consumer. It certainly does not mean 'I am Will.'"
Pharrell is asking the judge for written permission to continue using his "i am OTHER" mark.
It looks like the issue of who exactly owns the phrase "I AM" is about to get ugly. Will.i.am has filed a counter-lawsuit against Pharrell, who had previously filed a suit asking the judge to protect his use of "I AM," only after Will first fired a cease-and-desist letter to Pharrell for starting his "i am OTHER" brand.
Will notes that Pharrell founded a label called "Star Trak Entertainment" (you can probably guess what Will compares that too), Will states the producer is currently facing a lawsuit from Marvin Gaye's family over "Blurred Lines" similarities to "Got To Give It Up," plus he cites that Pharrell attempted to trademark Pink Slime, which apparently is a copy of the Slime brand owned by Mattel-- at least Will seems to think so.
Will.i.am states that if Pharrell uses the "I AM" slogan it will confuse people, because they are on the same record label and they make similar styles of music (they do?). Will.i.am is seeking compensation from Pharrell.