This "white glowing background" thing gets me oddly nostalgic, a lot of cartoons and anime I used to watch used this at some point and for some reason I always found it quite nice.

From what I can gather, it's alternatively known as underlighting, backlighting, and bipack glow: basically the animators just leave a hole in the background and shine a light through it. You could also insert stuff like color gels or tubes of glitter mixed in soapy water to add additional color and texture. In addition to its ubiquity in '80s and '90s animation, it was also used for certain special effects in live-action films in the '70s and '80s: for instance, it's where the Star Wars original trilogy got its lightsabers, blaster fire, and force lightning, as well as where the first Tron film got the glowing suits (among other effects).

It pretty much died out after the rise of CGI and computer animation. It's understandable why it's no longer used in live-action productions, but it's a shame that the art of it was lost in the animated realm, because it's something that you can still do in digital 2D animation by recreating the setup in a 3D modeling program like Blender.