Just to either further clarify or muddy the situation, I was creating an RFI Content type based on Document and had added about 20 columns to that type. I changed the Title to RFI Subject in the content type from Documents and it changed every Document Title column to RFI Subject. When I changed the Title from _Hidden to 'RFI Content Type', SharePoint added all those 20 columns to my Document and Item base types, which then added them to multiple web parts throughout my site collection.
So, in this case, I was creating a content type with Document as the base type. However, when I changed the Title from _Hidden to RFI, it changed not only the document content type, it changed the Item content type, which caused everything that used those types: discussions, libraries, custom lists, tasks and calendars to have an RFI Subject instead of Title in the lists along with all the additional columns. Obviously, this was not my desired outcome.
My solution was to go into the SQL Database, ContentTypes table and find the rows with "%Title%" in them. With some further searches, I found the rows with Name='Title' and StaticName='RFI Subject' and change the RFI Subject back to title. I also had to change the document type in the line from 'RFI Content Type' back to _Unknown in one line. I removed the extra columns from Item and Document types but that still didn't fix the web parts. This corrected the core problem so any new sites or web parts would not
have the extra columns, but it did not change the existing screwups. Since this was a brand new site collection, I deleted most of the corrupted web parts and modified the ones already in use throughout the site collection. It took the better part a workday to fix it all, but it did work and it would've cost me several days to start from scratch.
Reference: http://www.jwc3.net/2008/06/change-title-content-type-field-oops.html (This is the site that got me going in the right direction on this issue.
Hope this clears it up. However, I wonder if there's an easy way using either Visual Studios or SharePoint Designer to edit or delete those columns. SD lets us copy but did not seem to have a way to edit the web part columns directly.
Red.