Vegemite or Green Bean Casserole?
Vegemite is great as a "sandwich" ie really just toast as long as you don't slather it on thick like it's peanut butter or jelly like most Americans who don't know what to do. If you do it Aussie style where the toast is thick with butter and you put a pea sized or a little bigger amount to in essence flavor the butter it's one of my favorite toasts. I'll frequently do a light brekkie of one Vegemite "sandwich" and one with either peanut butter or one of my homemade jellies.
British style Marmite which is what you get everywhere other than Oz and Kiwiland is nowhere near as good as Vegemite for toast purposes as it's more like a thick syrup than a peanut buttery spread. But IF you can get actual New Zealand made Marmite it's the best. It's got the same lighter flavor of the British Marmite but they make it spreadable like their neighbors Vegemite. But I don't pay to import the better Kiwi Marmite, it's not THAT different from Vegemite where it's worth the cost difference.
As far as green bean casserole sandwiches...I've seen them and never ordered them. Usually I believe they throw in turkey with it which would make it more of a "real" filling sandwich. Now a day after thanksgiving sandwich of leftover turkey, dressing, gravy and cranberry "jelly" with a thin layer of Miracle Whip (turkey and/or deli sliced chicken sandwiches is the only time I use MW over Dukes or Kewpie Mayo) is tastier to me than the separate items fresh on Thanksgiving.