In the original film as well as the remake, Nikita murders someone and is found guilty. In the TV show, she did not murder anyone, and is found guilty anyway.
In the first episode of season one, "Nikita", footage taken from the movie Point of No Return (1993) is used while Nikita is sliding down the garbage chute when she's in the restaurant.
The show ran five seasons. The season number determined the number of words in an episodes title (i.e., all third season episodes had three words in their title).