Thank you so much! Exactly what I needed. I found a few more needing to be included, like adopts_folders_messages and adopts_pounds. There might've been one more I'm forgetting about because I didn't need to include it since the member wasn't in it lol.
For the forum, in case anyone else needs this, these are the only tables I think that needed to be included. Luckily most of them just store the user's ID:
Code:
UPDATE `mybb_forums` SET `lastposter` = "newname" WHERE `lastposter` = "oldname";
UPDATE `mybb_threads` SET `username` = "newname" WHERE `username` = "oldname";
UPDATE `mybb_threads` SET `lastposter` = "newname" WHERE `lastposter` = "oldname";
UPDATE `mybb_users` SET `username` = "newname" WHERE `username` = "oldname";