Okay I think I have unique healing items for the All Star Rest Area idea.
Mario franchise: Star Candy (Bowser's Inside Story)
DK franchise: Golden Banana (Donkey Kong 64)
Yoshi franchise: Super Happy Heart (Yoshi's Story)
Wario franchise: Garlic cloves (Wario Land: Shake It!)
LOZ franchise: Heart Container (Every Zelda game)
Metroid franchise: Energy Tanks (Every Metroid game)
Kid Icarus: Not sure (Don't know if Pit has a healing item)
ROB: Batteries (Since he is a toy that runs on a lot of them)
Ice Climbers: Vegetables (Like on The Summit in Brawl)
Kirby franchise: Maxim Tomatoes (Every Kirby game). Here, though, they heal like they did in Smash 64.
Pikmin franchise: Pikpik Carrot bunches (Pikmin 2)
Starfox: Not sure (they don't usually stop for lunch, ya know?)
F-Zero franchise: Fried Chicken (just cuz)
Pokemon franchise: Sitrus Berries
Fire Emblem franchise: Not sure (never played it before)
Mother franchise: Steak (Earthbound)
Mr. Game and Watch: Blob of Subspace (since he is made of the stuff)
Metal Gear Solid: Not sure (same reason as FE)
Sonic franchise: Chili dogs (they are his favorite food)
I need help with Kid Icarus, Starfox, Fire Emblem, and Metal Gear Solid. Any ideas?