Help with wrapping character with CSS span using Jquery
Two things I can think of that could possibly cause the problem:


Your code runs before the document is fully loaded. To fix it try wrapping the function call inside $(document).ready:

$(document).ready(function() {
  $('div').wrapInTag({
    words: ['™'],
    tag: '&lt;span class="trademark"&gt;'
  });
});

The CSS style are being overridden. Quickfix would be to add !important at the end.

.trademark {
  font-size: 9px !important;
  vertical-align: top !important;
}