John had a fairly pleasant speaking voice, lying in either the high baritone or low tenor range. Myers notes that many have pointed out John's tendency to stammer, "caused no doubt by ideas coming faster than his vocal apparatus could handle them" but also to chuckle at his own witticisms or laugh heartily at someone else's. John talked clearly, fairly rapidly, and fairly loudly. If there were an audiotape of conversation in a crowded room, his voice would definitely stand out, notwithstanding a certain shyness and reticence at social events or unfamiliar occasions. His accent was Standard American with perhaps only the slightest Midwestern inflection.

John's stuttering was noted by one of his college professors in Chicago, who notes in John's college placement booklet that:

"he has...two drawbacks...first is a tendency to stammer in situations of nervous tension; this handicap, however, is, indeed, more a personality trait than a pronounced handicap."

Another professors notes that:

He is, however, rather nervous, and because of this sometimes gives the impression of being less in command of a subject that he really is. My guess, however, would be that this nervousness will diminish and his poise increase.

Pat Thomas, one of John's students at Shimer College, recalls that John stammered "especially when nervous" and did not immediately make a great impression as a classroom lecturer. She describes Bellairs as a bundle of tics, bobbing his head, stuttering, and blinking rapidly in situations where he wasn't at ease. "Fortunately, our classes were supposed to be Socratic discussions, and in this he excelled. His extraordinary memory for detail and his encyclopedic interests made him a natural for this type of interaction with students, aided by his wonderful sense of humor."

"One way he got around his tics was to switch into the voices of different characters, as a way of saying things that might otherwise be difficult for him to say. Robin Williams does this best, but John was pretty good at it."

Myers agrees: "he loved to tell stories with a dramatic flair and would assume the accents of the characters in them if they were within his vocal range, but he'd give himself away on comic stories by chortling himself before he got to the punch line. One minor but hilarious talent that John developed in later years was a spot-on imitation of Bobby Kennedy. He had the Boston accent down pat, delivered with the slightly swishy lilt that distinguished Bobby from JFK."

John apparently had a varied range of television viewing: besides "The A-Team," John admits to watching a serialized version of Dickens’ Bleak House.

"I have to come up with a big zero on the subject of John's favorite television programs,” says Myers. “During our college years neither one of us watched much TV at all on a regular basis. In those pre-transistor and pre-chip days, television sets were too big, bulky, and expensive to lug around to a college dorm. Although the Notre Dame residence halls and the International House in Chicago all had television lounges, we would only bother with them for special programs - such as Oscar Night.”