The ending of the story—in which Jack re-embraces his Chinese heritage and realizes how deeply he loved his mother—is a tragic example of situational irony. After spending almost the entire story rejecting his mother (and her Chinese language and culture), including choosing to go back to college instead of spending time with her in the final days of her life, he surprises readers by getting in touch with his love for her years after her death.
The final lines of the story—which come after a Mandarin-speaking stranger translates a long letter Jack’s mother wrote to him before she died—captures Jack’s ironic change of heart:
The young woman handed the paper back to me. I could not bear to look into her face.
Without looking up, I asked for her help in tracing out the character for ai on the paper below Mom’s letter. I wrote the character again and again on the paper, intertwining my pen strokes with her words.
[…]
Following the creases, I refolded the paper back into Laohu. I cradled him in the crook of my arm, and as he purred, we began the walk home.
Here, Jack demonstrates care for his mother for the first time in the story by asking the stranger to help him write the Mandarin character for “love” and then writing it “again and again on the paper, intertwining [his] pen strokes with her words.” The intertwining of Jack’s pen strokes with his mother’s words symbolize the closeness and connection between the two of them in this moment, despite the fact that his mother is dead. The fact that Jack then refolds the paper back into the shape of the paper tiger his mother made (the first origami animal she ever made for him) and carries the tiger home “in the crook of [his] arm” also signals that Jack is intentionally embracing his mother's Chinese heritage for the first time.
After Jack’s white friend Mark demeans Jack’s mother’s handiwork—describing her origami animals as looking like they're made “from trash”—Jack rejects his mother’s Chinese heritage, ultimately hiding the animals she made him in a box underneath his bed. In an example of situational irony, Jack learns years after his mother’s death (via his girlfriend Susan) that his mother was an exceptional origami artist, as seen in the following passage:
Susan found the shoe box in the attic. The paper menagerie, hidden in the uninsulated darkness of the attic for so long, had become brittle, and the bright wrapping paper patterns had faded.
“I’ve never seen origami like this,” Susan said. “Your mom was an amazing artist.”
Despite the fact that the origami animals had become “brittle” and “faded” over the years, Susan can still see that Jack’s mother’s handiwork is exceptional, noting that she’s “never seen origami like this” and that Jack’s mother must have been “an amazing artist.” Jack’s mother later confirms this in a letter she wrote Jack before she died, in which she states that the region of China where she grew up was “famous for its zhezhi papercraft,” and she learned the craft from her mother at a young age. The fact that Jack's friend called the origami animals "trash" is therefore ironic, since they're clearly examples of his mother's impressive artistic talent.
It is notable that Jack only comes to appreciate his mother’s artistry after someone else is able to see it. This is one of the many times in the story when Jack prioritizes the opinions of his American peers over his Chinese mother’s, a harmful impulse that he later comes to regret.