Snicky [@puyonifyyyc](/images/2857558#comment_10078685)
Yes, if you check the tag description it has certain tags under "Implies". Lots of tags do this, like adding "diapinkies" will automatically add the "Pinkie Pie" tag.
This tag existed before g5 was announced and was specifically made for the Celestia and Luna pairing. You can go to the forums and suggest either a change to the tag's functionality or a rename of it.
To change the tags, click the "Tags: " box right above the rest of the tags, then simply click on the X of the tags you don't want (or type in new tags you'd like to add after posting). Anyone can do this if they see an error, even if they are not the uploader.