Much of the humor in Ovid's erotic poetry is cynical, ironic, and mocking. Sometimes, however, in other works, his humor is gentler and more playful, as in the passage from The Metamorphoses in which Peneus tells his daughter Daphne, that he wants her to marry:
Her father often said ‘Girl, you owe me a son-in-law’, and again often ‘Daughter, you owe me grandsons.’ But, hating the wedding torch as if it smacked of crime she would blush red with shame all over her beautiful face, and clinging to her father’s neck with coaxing arms, she would say ‘ Dearest father, let me be a virgin for ever!’ (A. S. Kline translation)
Here the humor is tender and loving.
For a good discussion of Ovid's humor, follow this link:
This is a great question. It can be strongly argued that humor is everywhere. One classical scholar stated that when she read Ovid, she does not know whether to laugh or cry. This is because in Ovid's works humor is everywhere. Let me give a few examples. First, in his work, the Art of Love (Ars Amatoria), he recommends men to go to the games to pick up girls. He writes Ars Amatoria 1.4:
"if by chance a speck of dust falls in the girl’s lap,
as it may, let it be flicked away by your fingers:
and if there’s nothing, flick away the nothing:
let anything be a reason for you to serve her.
If her skirt is trailing too near the ground,
lift it, and raise it carefully from the dusty earth:
Straightaway, the prize for service, if she allows it,
is that your eyes catch a glimpse of her legs."
The art of seduction is his point. What make this even funnier is that he is writing when Augustus is trying to make moral reforms!
Here is another example, in his Metamorphoses, he has the gods falling over human girls and nymphs all the time. Apollo the great god fall head over heels for Daphne, who by an act of kindness of the gods was turned into a tree before Apollo could rape her. Read these lines for a good laugh from the Metamorphoses book 1:
"Phoebus admired and loved the graceful tree, (For still, though changed, her slender form remained) and with his right hand lingering on the trunk he felt her bosom throbbing in the bark. He clung to trunk and branch as though to twine. His form with hers, and fondly kissed the wood that shrank from every kiss. And thus the God; “Although thou canst not be my bride, thou shalt be called my chosen tree, and thy green leaves, O Laurel! shall forever crown my brows, be wreathed around my quiver and my lyre;"