PPT 2016, Windows 10

To replicate:

1. Create a rectangle with appear animation
   1a. Create a rectangle by going Insert > Shape > Rectangle
   1b. While rectangle is still selected, add appear animation by going Animations > Appear.
2. Open E-Learning Lab PowerPointLabs > E-Learning Lab. There should be an appear animation.
3. Delete the rectangle while it is selected.
4. Click Sync on the E-Learning Lab pane.
5. Repeat steps 1 to 4.
6. Undo by pressing Ctrl+Z. There will be an unknown shape that appears after the undo operation.
   

On closer inspection, the name of the Shape is PPTL_Storage.