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.