MS-Excel 2013 Drag and Copy Issues

Using MS-Excel 2013, how do you prevent the drag and copy feature from changing the text automatically as you drag a cell down? For example, I type "OB" and drag the cell down to copy it, and it automatically copies the following: OB OB IB IB " " OB OB IB IB " " Keeps doing this repetitive pattern over again, even when entering either "IB" or "OB" individually and then dragging it down.

Is this related to the Flash Fill feature? Or perhaps within the Excel settings?

What should be copied, normally, would be entering "OB" dragging it down and getting only "OB"s in the cells below. Or visa versa when typing "IB". When typing any other letters and dragging them down, it seems to work correctly. this issue is only with Excel 2013.

Thanks.

After you drag-copy by grabbing the lower-right corner of the cursor, you'll see an icon will appear beneath the last copied cell. Click the icon to open a pop-up menu that allows you to change how the cells were copied. Screenshot below. Select "Copy cells" instead of "Fell series"

One interesting note here: When I tried to reproduce this by typing "OB" in cell A1 and drag-copying with cursor, it copied the cells without filling the series by default and "Fill series" was not even an available option. This is happening either because I more often change it to "Copy cells" and Excel is remembering my preference or because of changes I made to the default paste options.

Although this might be an overly simplified answer... in grabbing the lower right corner of the cell you're wanting to copy & paste- just hold down the Alt-key when you drag. This insures Excel doesn't add or look for a series combination to input. When in doubt, use the Alt-key to keep your data from changing.