[jquery] Can a table row expand and close?

It depends on your mark-up, but it can certainly be made to work, I used the following:

jQuery

$(document).ready(
  function() {
  $('td p').slideUp();
    $('td h2').click(
      function(){
       $(this).siblings('p').slideToggle();
      }
      );
  }
  );

html

  <table>
  <thead>
    <tr>
      <th>Actor</th>
      <th>Which Doctor</th>
      <th>Significant companion</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td><h2>William Hartnell</h2></td>
      <td><h2>First</h2><p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas.</p></td>
      <td><h2>Susan Foreman</h2><p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.</p></td>
    </tr>
    <tr>
      <td><h2>Patrick Troughton</h2></td>
      <td><h2>Second</h2><p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas.</p></td>
      <td><h2>Jamie MacCrimmon</h2><p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.</p></td>
    </tr>
    <tr>
      <td><h2>Jon Pertwee</h2></td>
      <td><h2>Third</h2><p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas.</p></td>
      <td><h2>Jo Grant</h2><p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.</p></td>
    </tr>
  </tbody>
</table>

The way I approached it is to collapse specific elements within the cells of the row, so that, in my case, the row would slideUp() as the paragraphs were hidden, and still leave an element, h2 to click on in order to re-show the content. If the row collapsed entirely there'd be no easily obvious way to bring it back.

Demo at JS Bin

As @Peter Ajtai noted, in the comments, the above approach focuses on only one cell (though deliberately). To expand all the child p elements this would work:

$(document).ready(
  function() {
  $('td p').slideUp();
    $('td h2').click(
      function(){
       $(this).closest('tr').find('p').slideToggle();
      }
      );
  }
  );

Demo at JS Bin