I've heard people allude to writings of some of Aristotle's students alleging bad character of Aristotle. I've not found the actual writings or any secondary literature on them. Can someone point me in the right direction?
John M. Dillon / Orality in the Later Platonist Tradition/ mentions a tale "related to us by the late (2nd c. A.D.) antiquarian and collector of miscellaneous tales Claudius Aelianus, but it may well derive from a more nearly contemporary source, the 3rd c. B.C. purveyor of malicious gossip Antigonus of Carystus":
Plato did not approve of [Aristotle]'s life and habit, for Aristotle wore rich garments and shoes, and cut his hair after a manner not used by Plato : He also wore many rings for ornaments; he had a deriding kind of look, and was peremptory in discourse : all which mis-became a Philosopher. Plato seeing this rejected him, and preferred before him Xenocrates, Speusippus, Amyclas, and others; to whom he shewed respect, and admitted them to his conversation. On a time, Xenocrates being gone into his Country, Aristotle came to Plato, accompanied with a great many of his Disciples, of whom was Mnason the Phocian, and the like : Speusippus was then sick and unable to be with Plato : Plato was fourscore years old, and through his age his memory much impaired. Aristotle assaulting and circumventing him by propounding arrogantly some questions, and arguing with him, discovered himself injurious and ungrateful.
We have bare-bones information about Aristotle's character from various ancient sources. As to his personality reliable information is harder to come by.
Criticisms of Aristotle's personality were mounted systematically for the first time by Diogenes Laertius in his 'Lives' (3rd century CE). Not only is there a gap of centuries between Diogenes and Aristotle - no contemporary observation here - but also Diogenes' biography of Aristotle 'recycles a good deal of gossip and scandal; the portrait of Aristotle in particular is riddled with damaging allegations' (Gary Ianziti, 'Leonardo Bruni and Biography: The "Vita Aristotelis"', Renaissance Quarterly, Vol. 55, No. 3 (Autumn, 2002), pp. 805-832: 812.) Diogenes appears to have had an animus against Aristotle and to have been less than precise and discerning in his search for and interrogation of authentic sources.
I don't want to get into a scales of truth exercise in assessing Diogenes but it may help answer your question if I mention a couple of points which relate to the 'bad behaviour' claim:
To begin with, Diogenes portrays Aristotle as an ungrateful pupil: "He seceded from the Academy while Plato was still alive. Hence the remark attributed to the lat- ter: Aristotle spurns me, as colts kick out at the mother who bore them. Next, Diogenes relates several stories concerning Aristotle's stay at the court of the tyrant Hermias. One of these stories was that Aristotle was the lover of Hermias. Another, told by Aristippus, had Aristotle so madly in love with a concubine of Hermias that he made sacrifice to her, as if she were one of the gods. Aristippus also related that Aristotle composed a hymn in praise of Hermias, which Diogenes faithfully reproduces in full. Diogenes also reproduces an epigram of Theocritus of Chios, in which Aristotle is accused of lasciviously dwelling with Hermias, all the while lifting hymns of praise to the tyrant. According to Diogenes, these very accusations lay behind the charges later brought against Aristotle in Athens at the end of his life. Diogenes has him fleeing Athens in disgrace, without having answered his accusers, then committing suicide by taking poison at Chalcis. Diogenes transmits this information and much more. His account is laced with alternative versions. His Lives should be regarded as a great collection of lore, catalogued and passed on almost in its raw state, the wheat with the chaff, the slander and innuendo. (Gary Ianziti, 'Leonardo Bruni and Biography: The "Vita Aristotelis"', Renaissance Quarterly, Vol. 55, No. 3 (Autumn, 2002), pp. 805-832: 813-4.)
(The Vita Aristolelis is Leonardo Bruni's (c. 1370 – March 9, 1444) life of Aristotle, written in 1429.)
I do not support any of these criticisms - Diogenes is too unreliable a reporter - but if you are looking for a historically influential source of allegations of bad character on Aristotle's part, Diogenes is a prime candidate even though Aelian's ''Varia Historia'' - see valuable answer above - is earlier than Diogenes' ''Lives''.