I once installed the "Forever Floyd" persona. I then installed a few other personas to change out as I felt like. After having the "Forever Floyd" persona enabled for a few months, I disabled it and enabled another persona I had installed. The newly enabled persona showed but only until I logged out of Firefox. The next time I logged onto Firefox, the "Forever Floyd" persona would show again. I then not only disabled the "Forever Floyd" persona, I deleted the persona entirely. Now it doesn't even show up in my appearance list when I'm in Add-Ons Manager but it still keeps showing up as my persona each time I log into Firefox!