How to override theme function to alter breakout fields?

(This may be all moot at this point, since you found the issue with Views Custom field, but I think it's decent information nonetheless.)

In general, you override a theme function by writing another version of the theme function with your modifications. There are the three levels for theme functions: theme_ , engineName_, and themeName_. When a theme function is called through theme('function'), Drupal looks for themeName_function() and uses it if it finds it, if it doesn't it looks for engineName_function(), and if that doesn't exist, it uses the default implementation, theme_function().

So if you are using a theme called "mytheme", you could write "mytheme_views_slideshow_thumbnailhover_breakout_teaser()", and Drupal will use it when that theme is selected. (The prefix "theme_" gets replaced with the name of the theme, "mytheme_".) Your starting point would be to copy "theme_views_slideshow_thumbnailhover_breakout_teaser()" from views_slideshow_thumbnailhover.theme.inc and put it in template.php, changing the function name.

If you are not using a custom theme but a contributed theme, and you do not want to modify the theme files, then you have the option of using the theme engine name. The default engine name for Drupal 6 is PHPTemplate, so your function would probably be named "phptemplate_views_slideshow_thumbnailhover_breakout_teaser()". This function would override the "theme_ "function. (However, a "mytheme_" function would override that.)

Using a bit more complicated approach, you could override the theme function with a module function. Normally, "mymodule_function" would not be recognized and override the theme function, but it is possible to change the theme registry and tell Drupal what function to use, using hook_theme_registry_alter(). The registry is an array of theme functions and templates, and you can manually add and remove values as needed. So in mymodule, you could write function mymodule_theme_registry_alter(&$theme_registry) and redefine $theme_registry['views_slideshow_thumbnailhover_breakout_teaser']['function'] to be "mymodule_views_slideshow_thumbnailhover_breakout_teaser" The hook_registry_alter would run regardless of which theme is being used, so it would override anything else.

Regarding your other question, I believe that the node_load() will indeed get the cck fields you need, but I don't know where. Since you already are running Devel, I suggest going to /devel/php to execute some php and write something like:

$nid = 123;//The node id of an example node to work with
$node = node_load($nid);
print_r($node);

Then you can see exactly what that node_load gives you. (Although, as the TODO: on that line says, the node_load does load too much. From a performance standpoint, it would be better to loop through the $view->result, collect all the $node->nid values, and write a query to get just the information that is needed - the node titles and whatever else you need.)