Teachers, also referred to as Masters, are the characters that lead the protagonist, Parappa or Lammy, through their stage. In video game terms, they function as both guides as bosses, as you are dependent on them to pass a level as well as needing to 'defeat' them in order to move on.
What Teachers actually are is arguable. Although appearing as regular adults, they were given somewhat of a spiritual essence in UmJammer Lammy.
In PaRappa The Rapper they appear as grown-ups of a certain profession that is relevant to what Parappa needs.
- Parappa wants to be tougher, so Chop Chop Master Onion learns him karate.
- Parappa wants a license, so Instructor Mooselini teaches him how to drive.
- Parappa needs money, so Prince Fleaswallow gives him a job to earn money.
- Parappa needs a cake, so Cheap Cheap teaches him how to bake one.
- In stage 5, they function as an obstacle and do not have a desire to help you.
- In the final stage, they give back to all your efforts, and hold a party in your name. You still have to rap correctly, but the atmosphere is more aimed at having fun.
In Um Jammer Lammy her teachers are vague in intentions, and the teachers of the previous game have become something demigod-like.
CCMO, Mooselini, Fleaswallow and CCCC appear in an imagination within a dream of Lammy when she tries to think up an excuse for arriving late. She meets CCMO on stage, where he trains her, predicts her future and leaves her with a mantra that would trigger her into regaining confidence. Before every stage, she is triggered by the word "casino" and remembers his words. Having been present through the entire game, he supposedly appears in flesh at Lammy's gig, but no mention of this fact is made. Due to the Stage 1 being Lammy's dream, it was not playable for Parappa in the game. It was however available in UmJammer Lammy NOW!. CCMO remembers Parappa, speaking with affection when he voices he's proud of him and Parappa (painfully naive) asks how CCMO has been.