Template Variables with preprocessor functions and customizations

In Drupal 6 the variable creation logic lives in the /includes/theme.inc file. The functions of note, located at the bottom of the file, are: * template_preprocess * template_preprocess_page * template_preprocess_node * template_preprocess_block These preprocessor functions can be used for altering variables in their areas. By browsing the function definitions you'll see how the variables are created.