I believe I do have a timeline of events that you might find revelatory.
When asked by Jerry, Uncle Newt explains that a paean is “a long poem about how wonderful you are”. Jerry asks if he can have one. Uncle Newt tells him that he can maybe have one for his birthday.
They wish each other goodnight, to which Jerry adds: “Don’t let the bedbugs bite.”
After first hearing Jerry’s latest poem, for which Jerry is paid his standard ha’penny, Uncle Newt gives him his birthday presents.
Jerry opens a gift to find a kazoo, which Uncle Newt admits he had just found at the back of a drawer.
Uncle Newt encourages Jerry to blow the kazoo, which cues Newt to deliver a “paean of praise” that he has written for Jerry. The paean tells of Jerry’s accomplishments and good deeds while living with his uncle.
Unbeknownst to Jerry, his mother, Vanessa, has taken leave from her war service, so that she can visit. She arrives in the room as Uncle Newt is finishing his paean. She delivers the final word: “Surprise!”