The story of The Swan Princess is inspired by the famous ballet of Swan Lake, which tells the tale of a princess who is enchanted by a sorcerer to take on the form of a swan by day, and only returns to her human form at night. The only way this enchantment can be broken is if the princess finds true love. The Swan Princess, released in 1994, takes that central story and gives it that fluffy touch, filled with sweetness and heart.
The main characters in The Swan Princess are Princess Odette and Prince Derek, who have been betrothed together by their parents King William and Queen Uberta respectively. Odette and Derek don't grow up the best of friends, but when they reach adulthood see each other in a different light and fall in love. It looks like a marriage is on the way, but when Derek accidentally says the wrong thing (praising Odette's beauty but little else), she declares the whole thing off. Derek realizes he made a mistake and wants to fix things, but before he can, the Wizard Rothbart whisks Odette away without a trace.
Rothbart is keeping Odette at Swan Lake, and swans happens to be the method of imprisonment he uses on Odette. Technically she is free to go wherever she wants, but he has placed a spell on her that transforms her into a swan by day. If, at night, she wishes to become human, she needs to sit on on the lake and when the moonlight touches her wings, she will be restored. Until sunrise, that is.
But neither Derek nor Odette are giving up. Derek believes Odette is still alive and seeks to find her, while Odette teams up with her new animal friends Jean-Bob the frog, Speed the turtle and Puffin the bird, to figure out a way to get back to Derek. It goes without saying that all the good guys end up living happily ever after. (Or at least, until the sequels.)
On the left here is the first cover of The Swan Princess when it was first released on video. Most promotional activity for the movie back in 1994 used this image or something similar to it. This poster happens to be favourite of mine, since I think it captures the feel of the movie beautifully, and has a whole bunch of characters on it while still giving prominence to the couple.
Some video releases of The Swan Princess came with two "hidden" extras: a music video of Dreams Come True's Eternity and a brief The Making featurette. Both of these come on after the end credits, so if you have the movie on video, be sure to check if your version has these extras.
Later releases of The Swan Princess, whether on video or DVD, have different images from the original, some of which are:
The Special Edition DVD, which was released as part of the movie's 10th Anniversary, contains some new extras in the form of a read-along feature and some games. Many thanks to Prince for sending in the picture of the Collector's Edition video.
After the original, there were three sequels made, giving the full Swan Princess series four films in total. The second and third films are traditionally-animated, just like the original, and the fourth film is computer-animated.
The Swan Princess II has the subtitle of The Secret of the Castle or Escape from Castle Mountain. From what I can make out, the American title of the movie is Escape from Castle Mountain, but in most places in Europe and Asia, it's known as The Secret of the Castle. Anyway, this sequel was released direct-to-video in 1997. There are a few different covers for The Swan Princess II, but the content appears to be the same.
In this movie, Rothbart's old partner, Clavius, is after the Forbidden Arts that he'd developed with Rothbart. Apparently Rothbart left an orb containing the dark magic hidden deep within the Swan Lake castle, and Clavius hatches a plan to distract Derek and sneak into the castle, so he can take become the most powerful sorcerer and take over the kingdom.
The Swan Princess 3 is in a similar situation with the previous sequel in that it seems to have two names. Depending on where you are, it's either known as The Mystery of the Enchanted Kingdom or The Mystery of the Enchanted Treasure. (Though "treasure" makes more sense in terms of the story.) It was released direct-to-video in 1998, not long after The Swan Princess II. It has since also been released on Special Edition DVD, though with what extras, I don't know, because I don't have that version.
In the third movie, Zelda, a different former partner of Rothbart comes out of the woodwork. She's after the written spells that Rothbart used to create the Forbidden Arts, so that she may have the power to create, change and destroy things at will. Her plan involves romancing Rogers so she can enter the castle and find where Derek hid Rothbart's old documents.
A fourth movie in the series, A Swan Princess Christmas was released in 2012, eighteen years after the original. On the surface there's a huge change because it's computer-animated, and Odette gets a brand new voice after three films (Michelle Nicastro, who provided her original voice, passed away in 2010). That said, the film stays firmly within the canon of the previous films, even including some canonical bits that were forgotten, such as Odette's mourning her dead father, and how Odette isn't a native of Derek's kingdom and doesn't know the traditions of his people.
In this film Rothbart himself returns as a ghost, out to destroy the kingdom's Christmas spirit because that's a power greater than his Forbidden Arts. If he succeeds, he will become corporeal again, and fully powered up to take over the kingdoms as he desires. But Derek and Odette are there to stop him, and have enough love for each other and the kingdom to fight back.
Prior to the recent release of the fourth film, the first three have been released together as sets. There's a 2-sided-disc Euoprean set containing all three movies and the sing-a-long (the most left cover). There is also another release (the mostly-white cover in the middle), although I don't have any other info of this release. On the far right below is a cover of an alternate double-feature DVD containing The Swan Princess and The Swan Princess 3.