Tchaikovsky has a reputation for bringing high production values to the composition of ballet scores by conceiving them architecturally and symphonically. But in practice, he’s as likely to borrow, copy and paste from himself as much as anyone else, if not more. He was perhaps a bit better at disguising the joins.
For example, when the suite of dances originally envisioned by Petipa was thrown out of Act I of Nutcracker, Tchaikovsky harnessed some of them for the diverts in Act II, and one in particular – a tarantella in C minor – became the male solo of the Sugar Plum pas de deux. But this wouldn’t fit well between the G major of the adagio and the E minor of the Sugar Plum solo, so he transposed it into B minor, which is a close relative of both those keys.
When you think of it in C minor, you hear how close it is to the boys solo in the Act I pas de trois of Swan Lake. And when you think of it as those ‘Greetings from Italy’ national dances that should have been a divertissement elsewhere, it becomes easier to understand its shortcomings as the solo it should be in that pas de deux.