Trivia: One of the members of D-12 (Eminem's real life hip hop group), Proof, can be seen several times during the battles at the end of the movie, including at the end of the battle with Lickity. Proof is wearing a hat with the D-12 logo on it.
Trivia: The sheet of paper that Jimmy writes on on the bus is the real sheet that Eminem wrote "Lose Yourself" on. The sheet of paper sold for $10,000 on an eBay auction.
Trivia: During the movie Eminem shoots paintballs at a police car. In real life Eminem had his first brush with the law when he was 20...For shooting paintballs at a police car.
Trivia: Listen close to Lil Tic (played by Proof)'s verse at the beginning of the movie when Rabbit chokes. He says: "I'll Punish Rabbit Or Obsolete Future" as you can tell by reading the capital letters in those bars, Lil Tic spells out his real rap name, PROOF.
Trivia: The car that Eminem drives round in during the film is the actual car that was given to Eminem by his mother Debbie back in 1990. Proof even gave it a nickname: The Stinkin Lincoln.
Trivia: Right after Rabbit finishes his last verse and waits for Papa Doc to rap, he sits on this speaker or something. If you look behind him, you would see "Sara Stokes" from the show "Making the Band 2" cheering (also known as the "ONLY" singer in "Da Band").
Trivia: Obie Trice has a cameo in the scene where they're in some sort of parking garage. It's not as obvious as Xzhibit's, but his name is in the credits.
Trivia: Evidently, Eminem was somewhat hesitant to take on the role as he felt that the movie would simply devolve into a cheap star-vehicle if he signed on, due to his fame. He told director Curtis Hanson that he would do the film if rather than trying to make it into an "Eminem movie", they simply focused on just making a "good movie."
Trivia: Quentin Tarantino was approached to direct due to his adoration of African American culture and for his high quality track record. He was reportedly very interested, but had to politely decline due to scheduling conflicts with his film "Kill Bill."
Answer: They were just freestyling, that is not a real song.