Extra sheetnames and a workbook have appeared in my list of modules,sheets and workbooks

As I was working on an app, and for a reason I can't fathom, suddenly, my list of sheets, modules etc was nearly doubled. When I selected such a numbered sheet from this list all the new ones took on the name of the same existing sheet. There was no sign of any of these sheets being actually present in the work book. There was also listed a new workbook named workbook1. Unlike the new sheets this workbook did not respond to any left or right clicks.
My question is 1). will it be safe to delete the unwanted sheet names? and 2.) how do I remove workbook1 as it does not respond to a key click.
John