One high school lunch period, I pointed out to a friend of mine that plastic cutlery, or "plastic ware", could be handily contracted to simply "plastiware". For some reason he found this way more amusing than he should have. Some time later, he made a DeviantART post in which he referred to me, but as "Plastiware" instead of my real name. When I got around to making a DeviantART account of my own, I called it "Plastiware" so it'd be consistent with his references, and the name kind of spread to pretty much everywhere else too.
Before Plastiware, I used to go by "Lazor'd". This is a combination of two Homestar Runner references: One, Strong Bad gave a bunch of examples of band names one could create by misspelling real words in cool ways, one of them being "Lazor". Two, characters in Teen Girl Squad have a tendency to die by way of getting "something'd" (eg, "ARROW'd"). When I was creating an account on the old, now-defunct Homestar Runner Fanstuff Wiki, I combined the two into Lazor'd to create my username. I've since abandoned this username not only because "Plastiware" spread and took over as my go-to username, but also because of possible "lole meme" cringe factor as it could be mistaken as a reference to firing one's "lazor".
