I want to send the username of the person submitting the form along with form data
You don't pass $user to the submit function.

Instead, you add a declaration of the global $user object to the start of the submit function to bring it into scope.  Like this:

function input_simple_form_submit($form, &amp;$form_state) {
  global $user;

  // Display a message upon successful submission.
  drupal_set_message(t("Added @color @TV_Show", array(
    '@color' =&gt; $form_state['values']['color'],
    '@Name' =&gt; $form_state['values']['TV_Show'],
  )));
  $id = db_insert("TestForm")
    -&gt;fields(array(
      'color' =&gt; $form_state['values']['color'],        
      'TV_Show' =&gt; $form_state['values']['TV_Show'],
      'SubmitBy' =&gt; $user-&gt;name,
    ))
    -&gt;execute();
}