Tarian is portrayed by Jason Sims-Prewitt.
Principal Tarian is authoritative as a leader and is keen on enforcing policies. At the same time, he can be playful especially when it comes to his favorite pet turtle, Shelly.
In Quad Court, he is tired of getting pranked all the time. He later realizes that Mack has been the one pranking him. Later on when the Harper Quads frame Mack for spreading goff balls in the hallway, Principal Tarian is convinced that Mack did it despite the quads confessing. The quads even invite him to a Quad Court hearing where they're witnesses against themselves but he still thinks they're protecting Mack. He finally gets convinced when he sees Tom licking the golf balls.
In Nicky, Ricky, Dicky & Sicky, the Principal is part of the Edgewood staff in charge of the class field trip. He makes it clear that no one should go on the class trip if they're feeling sick. But Dawn convinces her brothers to let her come along anyway despite being sick. All the quads end up getting sick and spending most of the trip trying to hide from Principal Tarian. He later busts them and confronts them for it.
In The Buffa-Lowdown, Principal Tarian gets a group of students to be in charge of the Edgewood Buffa-Lowdown morning news cast. He promises to give them good grade if they keep doing a good job. His turtle Shelly gets a role in the newscast team as part of "ShellyCam." The ShellyCam mainly just shows people's feet since it's so low on the ground. When the quads mess-up a broadcast, they cut to ShellyCam catching Principal Tarian unaware. The camera shows him lying on the ground in his office playing with Shelly. After figuring out what happened, the principal gets mad at the team for ruin the newscast and threatens to give them a lower grade. However, the quads quickly come up with a lie, making him believe that it was all part of the show. He is impressed and agrees to give them an A+.
In Quadshank Redemption, he is organizing the school carnival. After making the quads say hello to Shelly, he accidentally drops a bunch of carnival tickets. The quads grab them and start fighting for them. Principal Tarian comes back and despite the quads attempt to convince him that they actually wanted to return them, he is convinced that they're up to no good. He gives them detention on the day of the carnival.