I'm not sure how your cat managed it, as the keyboard shortcut to do this is Ctrl + Shift + 8 I believe.
However, to put it back to normal, right click anywhere on the desktop, click view, followed by any option, EG Medium Icons.
EDIT: As there has been some interest, CTRL + SHIFT + number produces different views when used on any folder, including the Windows Desktop.
Extra Large Icons
Large Icons
Medium Icons
Small Icons
List View
Details
Tiles
Content
Tested working in Windows 10, Windows 8.1 and Windows Servers 2012 and 2016 (Hotkey may vary between editions, as it's reported to be Ctrl + Alt on Windows Server 2016 TP4 (Simplified Chinese))
