I've figured out a workaround by other codes found on google...
HTML Code:
<blockquote class="postcontent restore ">
<div class="bbcode_container">
<div class="bbcode_quote">
<div class="quote_container">
<div class="bbcode_quote_container"></div>
<div class="bbcode_postedby">
<div style="margin: 5px 20px 20px;">
<div class="alt2" style="text-align: right; margin: 0px; padding: 6px;">
<span style="float: left; padding-top: 2px;"> <img src="images/icons/icon-spoiler.png" alt="Spoiler" />
<b>Spoiler: <i>{option}</i></b></span>
<input value="Mostrar" style="margin: 0px; padding: 0px; width: 80px; font-size: 10px;" 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 = 'Ocultar'; } else { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = 'none'; this.value = 'Mostrar';}" type="button">
</div>
<div style="padding-top: 4px;">
<div class="alt2" style="display:none; margin: 0px; padding: 6px;">
{param}
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
Notice i'm using the OPTION tag, so be carefull
This will work for those threads with more than one spoiler, avoiding the load of the javascript (so if you do this, remove the code in headinclude)