I've been meaning to do a little post on this for a while, as I thought it was a cool little game to discover within Super Mario 3D World.
Luigi Bros is a Luigi themed remake of the arcade classic and NES game - Mario Bros. Play as Luigi and try to clear out the sewers of menacing Fighterflys, Shellcreepers and Sidesteppers (the names they used in the Commodore 64 version of Mario Bros) - if you play two player, one of you is normal Luigi and the other gets the Fire Luigi outfit, though you can't actually fire anything.
Every so often the sewer brawling is broken up by a test your skill round where you have to try and get all ten coins to score lots of bonus points; these bonus rounds also seem to give you an extra continue if you get all ten coins - they are at phase 3 and phase 8. There might be more, but I just don't have the madskillz to go on much past phase 16.
Find out how to unlock Luigi Bros here.
Does anyone know the total number of phases in this game? How far did you get?