If asked somebody who is Krishn, he would surely say - Bhagavaan Krishn. Krishn means Bhagavaan Krishn, and nobody else. It is true, but in Mahaabhaarat Bhagavaan Krishn is not the only Krishn. There are some other Krishn also. It is interesting to know that how many Krishn are in Mahaabhaarat --
(1) Krishn (God)
Naturally He is the Supreme God Krishn who was also named as Krishn by Garg Muni when he was invited to perform His naming ceremony. He is the first and main Krishn in Mahaabhaarat. Now let us proceed forward --
(2) Ved Vyaas - Krishn Dwaipaayan
Ved Vyaas Jee is the second Krish in Mahaabhaarat. Because Ved Vyaas is not his name, that is his position - Ved Vyaas means who divides the Ved. His real name is Krishn Dwaipaayan. His given name was Krishn and since he was born on an island, he was named Dwaipaayan, that is how his name is Krishn Dwaipaayan. So he is the second Krishn.
(3) Arjun - Krishn
Yet another Krishn. He is the third Krishn. Arjun's one name, out of his 10 names, was Krishn too, because his complexion was dark. Krishn means dark.
(4) Draupadee - Krishnaa
Yet another Krishnaa is Draupadee. She is also Krishn, but because she is a female her name is not Krishn but Krishnaa, still she is Krishnaa. When she was born she was also named Krishnaa, because she was also of dark complexioned.
(5) King Paundrak - Fake Krishn
All of the above were real Krishn, but this King Paundrak was also Krishn. He was neither real Krishn, nor he was named Krishn, but still he is known as Krishn - fake Krishn. He considered himself the real Krishn. He used to dress like Krishn, tried to look like Krishn and behave like Krishn. He challenged the real Bhagavaan Krishn to consider him as the real Krishn. Real Krishn accepted his challenge and killed him by His Chakra. According to Krishn Himself, He had gone to kill that Paundrak when Draupadee was facing the insult in Kaurav's Dice court. For the same reason Krishn could not reach there.
Thus in Mahaabhaarat there are 5 Krishn.