FE is "Fish Extender". Yes, that's a really strange term. You can find better explanations of it on the boards, but in a nutshell: there's a clip on the outside of your cabin door that's shaped like a fish. I'ts original intended use was to leave the cabin occupants a note. The nice folks here on these boards have organized a voluntary activity where they share their cabin numbers and some info about who's in the cabin. If you're participating, you hang something from that clip that can receive little trinkets from the other participants, hence FE or "Fish Extender". You go around to those cabins and drop off a little treat. It's like reverse trick-or-treating.
The link for the roaming gnome refererence is working, but there aren't any pictures or explanations on that thread page. I'll take a stab at explaining what the gnome is, but don't know exactly what they were doing with the gnome (probably just a magnet of the gnome) on the ship.
The travelling gnome prank is the practice of returning a garden gnome "to the wild". It involves stealing a gnome, taking it on a trip, and photographing it at famous landmarks, with the photos being sent to the owner.
This began several years ago, when someone took a garden gnome out of an Australian women's yard, leaving a note saying the gnome was off to see the world. She subsequently received pictures of the gnome in various locations.
http://en.wikipedia.org/wiki/Travelling_gnome_prank
A travel company here in the States heard of the prank and decided to feature the garden gnome statue in its commercials, calling it the "Roaming Gnome".
https://twitter.com/RoamingGnome
