At work I’m using the Dell Latidude E5500 notebook, running on Debian
testing. Today, I had some issues with Xorg which could not detect my
keyboard and mouse, so I tried to do the Magic SysRq tricks (you can
read about it at Wikipedia). Unfortunatley, to press SysRq (on
F10), I had to use the Fn key, so if I pressed e. g.
Alt+Fn+SysRq+U, the U was detected as keypad 4 because of
the Fn key. Luckily, it works as intended if you release the Fn key
after having pressed Fn+SysRq, so to remount all mounted filesystems
in read-only mode, you would actually hold Alt, hold Fn, hold
SysRq, release Fn, press U.
Never thought notebook keyboards were so smart 