When you try this at home, just be sure to submerge the metal part of the bulb in water. Don’t do it for more than 20 seconds. I hear they explode a bit if you leave it in longer. Different parts of the microwave affect it differently as you can see so that kinda makes it fun.
Actually people on youtube are doing it for longer so I guess it’s up to you. Also, CD’s look really cool when you put them in for about 5 seconds. Make sure you don’t want the CD anymore though.