Wookieepedia has a few meta templates, namely Iumb and Ooumb, that are hideable. They are used to make notice templates such as this one. The [show]/[hide]
button allows it to take up less space and be more mobile-friendly.
I've looked over at the source code for the templates, as well as the Common.css and Wikia.css files, but I'm not exactly sure which classes would allow me to produce a similar template on my wiki. Any help would be greatly appreciated.