"Sorry, am dumb..."
Boy is very nasally and ignorant of current events, in part due to his illiteracy, and in part due to the Imperium placing little emphasis on educating the common masses. Before working as a voxcast serf, he and his family made money selling greasy food to petitioners in the palace (while getting trampled frequently). However, he has been studying under Rogal Dorn, who has encouraged him to aspire to be more than a mere serf. In fact, he affectionately calls Dorn "Dadorable," after his wall-name of "Lord Adorable."
When asked what his name was, the boy took too long, so in his impatience the Emperor simply had him renamed as "Boy."
Whereas Rogal Dorn has taken to looking after Boy, the Custodes are ambivalent to his needs, especially Karstodes, who finds his presence obnoxious and threatens multiple times to eject him and/or snap his neck, though as of Day in the Life of Boy he appears to have gained a begrudging affection for him. For some reason, Boy is terrified of Cyberdong and believes him to be a harbinger of death, probably because of the skull that he wears.
Boy lost one of his eyes when Helbrecht smashed a teacup in his face. Despite this, he was able to perceive horrifying images through his missing eye due to the cursed book Inquisitor. Dorn was deeply troubled by Boy's trauma, but was hopeful that he could grow up to become stronger.
Boy was later interrogated by a vox cyborg with questions relating to his daily routine. The interrogation quickly turns sour as the cyborg finds Boy's answers to be either underwhelming or completely ridiculous, despite Boy's answers being perfectly normal if not more so than what the vox cyborg describes as being 'the norm'. Several questions in, Boy becomes frustrated for the first time by the cyborg's incessant interruptions to the point that after being silenced by duct tape and having his family threatened with death Boy lashes out at the cyborg, bashing him over the head repeatedly with his vox-caster and kicking his shin until the cyborg calls for the vox guard. Boy puts up a surprisingly good fight before having his ears explode due to a high-frequency sonic blast from the vox guard. Suddenly Karstodes appeared to bring Boy back due to him being late for the next vox-cast. The vox cyborg bled out due to a wound in his shin from Boy kicking them.
Boy also appears in the Paradox-sponsored "TTS Special 7: Space Game Pain" where the characters all play the strategy game Stellaris in a manner that (not-all-too) inaccurately depicts the events leading up to, during, and after the Horus Heresy. He plays the role of Boy, serving as the "war meister" who is portrayed very similarly to Horus. He displayed surprisingly brutal and effective battle tactics to the point where his initial crusade nearly steamrolled the galaxy. After Kitten won, he suggested playing Crusader Kings.
Boy appears to be a powerful psyker evidenced by the fact that when confronted by the rat god of the Skaven to join them he simply uttered “no” and proceeded to banish the god back to whence it came with seemingly no effort and then proceeds to simply fall asleep.
Boy finally appears outside of the Podcasts in Episode 29.
Boy portrays himself as a Molluscoid in "TTS Special 7: Space Game Pain" where they play Stellaris, albeit one housed in a suit of intimidating, evil-looking battle armor, emulating The Horus Heresy.