[Natch]

Bear with me:

[high]* Natch heads to his forum for this BBcode...
[/high]
OK: I'm back

That animesuki forum is using this BBcode: I think I found it on vbt, or here, some somewhere ...
Spolier BBcodes
Name: Spoiler Tags
Tag: spoiler
Replacement:

<div style="margin:5px 20px 20px 20px">
	<div class="smallfont" style="margin-bottom:2px"><b>Spoiler:</b> <input type="button" value="Show" style="width:45px;font-size:10px;margin:0px;padding:0px;" onclick="if (this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display != '') { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = '';this.innerText = ''; this.value = 'Hide'; } else { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = 'none'; this.innerText = ''; this.value = 'Show'; }"></div>
	<div class="alt2" style="margin: 0px; padding: 6px; border: 1px inset;">
		<div style="display: none;">
		{param}
		</div>
	</div>
</div>

Example: [spoiler]Darth Vader is Luke Skywalker's Father[/spoiler]

Simple as that it's a ver' sexy DOM manipulation, and it's pretty bulletproof...