When one asks another verbal mammal to spell iCup, they are attempting to humiliate said animal by getting them to speak the words: "I see you pee", to which
It started out as a way of Playground trickery and now has spiraled to an ironic meme. With the meme often containing images of a person with lens flares for eyes and the image being saturated beyond belief with the caption "Spell Icup".
The act of mockery against a certain NIBBA and making He feel uncomfortable because of his inability to spell Icup. But when He really can spell it, all surrounding NIBBAS get blown back because of dat NIBBA'S pronouncing skill. But if he don't do it, then he get beat up by his friends.
Person 1: Yo, spell Icup NIBBA Dat Nibba: I C U P
Literally Everyone Around: Yooooooooooooooooooooooooooooooooooooo