As you might have heard it happens more and more often that flightcrew are being 'shot' at by green lasers from the ground.
The results of getting such a beam of intense light in one's eyeball can be disastrous and leave permanent damage, and results can be even worse if this would happen during the last part of the approach or landing, as you can imagine.

As a joke, we thought we'd start shining back from the cockpit!
Of course, those green lights you see here aren't lasers, neither are they dangerous. ;)