Show div when radio button selected

I would handle it like so:

$(document).ready(function() {
   $('input[type="radio"]').click(function() {
       if($(this).attr('id') == 'watch-me') {
            $('#show-me').show();           
       }

       else {
            $('#show-me').hide();   
       }
   });
});

Input elements should have value attributes. Add them and use this:

$("input[name='test']").click(function () {
    $('#show-me').css('display', ($(this).val() === 'a') ? 'block':'none');
});

jsFiddle example

$('input[name=test]').click(function () {
    if (this.id == "watch-me") {
        $("#show-me").show('slow');
    } else {
        $("#show-me").hide('slow');
    }
});

http://jsfiddle.net/2SsAk/2/