[There is, in fact, a real life whip sword. Jane's kind of right about the practicality in that it's very difficult to wield, but it does exist and has for quite a long while. Granted, Allura's whip sword has very different mechanics behind it.]

Something like that, in this case. [Another toss, another bottle ringed.] It's a rather long story, but my father King Alfor was able to create five sentient spaceships, the Lions of Voltron, and they in turn created weapons for their pilots to use. The bayards respond to the user's personality and thoughts and can change shape.