One of the newest members of the Lawndale High faculty, he was lured over by Ms. Li from Fielding Preparatory Academy. Highly educated and of British birth, Phelps seems to embody the stereotype of the "proper priss," with a love of good tea and a steel rod up his bum. He is utterly disliked by most of the faculty at Lawndale High, especially DeMartino, who resents Li's favoritism toward him.
As noted by Jane (in "Charge of the Math Brigade"), Phelps demands a lot of his students. But he has taken a particular interest in Quinn, revealed as early as "Cheered Down." He pushes her to embrace math, explaining that she is one of the most naturally gifted students he has ever met and should be in the advanced classes ("Of Absolute Value"). He even goes so far as to put her on the mathletics squad. When Quinn asks him in "Tomorrow Never Knows" why he chose her instead of one of the better students, Phelps tells her that only Quinn knew instinctively how to solve a difficult problem without any prior instruction. Quinn resists his efforts at first, but grows to admire Phelps for his commitment.
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Daria, however, is suspicious of Phelps. She suspects that he may be manipulating Quinn, and possibly other students, for reasons that she cannot determine. From "Charge of the Math Brigade" onward, she investigates his suspicious behavior, fearful that he might cause her sister harm. Her search yields little, until she receives an e-mail from a Fielding Prep administrator ("Into the Fire"), asking her to meet with him. There, Marshall Winsett reveals "rumors" that Phelps conducted criminal activity using student accomplices.
Daria tries to warn Quinn, who dismisses her concerns as jealousy. After "Memory Road," Quinn spends more time with Phelps, viewing him as a stable father figure while her own family falls apart. Phelps, himself, seems increasingly fond of her as a person, stating in "Tomorrow Never Knows": "I wouldn't call her my 'daughter,' per se, but I do feel as though she's a part of me." He gives her a large extra-curricular math project to do, claiming that it will help her excel in the Advanced Placement exam for college-level math.
When he learns what Daria was told, the dark, ruthless side of his personality comes out.
Phelps in other fanfics
Wild also used Phelps as the villain in an alternate universe fic to her alternate universe series, "They Came from Planet Xulfanex." There, Phelps is virtually the same, personality-wise, and he has the same relationship with Quinn, until revealing that that he comes from another planet. From that point onward, the Phelps character in "Xulfanex" departs dramatically from the Phelps in the Driven Wild Universe. Although Phelps is similarly ruthless in the DWU, he is not willing to kill and does not have extraordinary powers like "Xulfanex" Phelps, particularly mind control. Phelps from "Xulfanex" also has much more of a history with Jake.
Fanfics by other fanfic authors have had Phelps cameos, including "Band Aid" by Admonisher and "Otherwise Known as Quinn the Great" by Austin Covello. Brother Grimace has also used Phelps in his fic After Work, and in the John Lane Series, a "Mr. Phelps" is mentioned as a LHS math teacher. To date, it does not appear that fanfiction authors have created any other well-known math instructors.
"You know something, Ms. Morgendorffer, you were right: we are two of a kind. We both are willing to do what we can to go that extra mile, whatever it takes to win. Just as long as we first put our eye on that finish line." -- Charge of the Math Brigade