I believe you need to copy the Stext template to the other wiki.

Basically you need to look at these 2 pages:

• http://steven-universe.wikia.com/wiki/Template:Stext?action=edit
• http://steven-universe.wikia.com/wiki/MediaWiki:Common.js

Don't forget the CSS too.

/*Spoiler tag*/
.spoiler.on {
    border: 1px dotted #D5D4D4;
    border-top: none;
    background: transparent !important;
    color: transparent !important;
    text-shadow: none !important;
    padding: 0 1.4px;
}
 
.spoiler.off {
    border: 1px dotted #D5D4D4;
    border-top: none;
    padding: 0 1.4px;
}
 
.spoiler.on a {
    color: transparent !important;
}
 
.spoiler.on img {
    visibility: hidden;
}

thanks, the css was the part that I was looking for (had no idea where to find it)