nerd teacher [books] quoted Have a Hot Time, Hades! by Kate McMullan (Myth-o-Mania, #1)
Think you know the real story behind the Greek myths? Think again. Most people only …
After a hard day, I like to go home to the palace with my dog. Don’t I, Cerberus? Yes, that’s my good old boy, boy, boy. (He has three heads, and he hates it when I leave one out.)
— Have a Hot Time, Hades! by Kate McMullan (Myth-o-Mania, #1) (Page 7 - 8)
I feel like the author missed a trick where they should've used 'they' over 'he', since it's a three-headed dog. Which is just more interesting to show wider grammatical usage rather than a statement on anything.