How to Resolve module-theme name collision

When someone is building a custom site it can happen that same name module and theme are being developed. This results in very weird behaviour from Drupal's side: overriding hooks can make your blocks disappear, print $content returns only 'array', hence disappearing admin interfaces which force us to alter the database to get back on track.

Now we have to find out how to remove the new theme and switch back to an old one. We are lazy people, moreover our site is big, with lots of content, so reinstalling is not an option. I tested this with mysql, so these hints are for mysql only.

Dump your database first, and save it somewhere safe so we have a backup. We are going to edit the dumped records, and reinsert the database. I used this method because using my favourite editor is way easier and safer than using mysql shell (anyway we shouldn't edit a live site database).

The theme name is registered in the following tables in your database: system, variables and block. After many tries I realised I have to clear the cache manually, meaning to remove all the INSERT INTO `cache_` lines in order to see results. Change the 'default_theme' value in `system`, where note that 's' stands for string length, so be sure you put the string length after the 's:'. Also make sure you change the value to an existing theme (available themes listed in `system`). And remove, or rename your troublemaker theme.

The change in `block` is imperative, otherwise the blocks will not appear. Drop your old database from the sql server and insert the edited one. Voila, we have recovered from a theme crash.