Toad Town
 - Sushie needed to access warp pipe to sewers in lake
 - Bombette needed to break rock on Dry Dry Railroad (could be just removed)
 - Bow needed to access Shy Guy's Toy Box (could just be always available)

Tunnels
 - Bombette needed to access Rip Cheato + Blue House entrance
 - Parakarry needed to access a Star Piece
 - Lakilester needed to access pipe to Ultra Boots (three entrances total)

Pleasant Path
 - Kooper needed to access a Star Piece and to hit a ! Switch to progress
 - Bombette needed to access a pipe to the top of the fortress (one entrance)

Koopa Bros Fortress
 - Kooper needed to reach ! switches leading to final rooms (maybe Parakarry could cross the gap too?)
 - Bombette needed to access entrance to key in cage, other key in cage, entrance to Refund, to exit the Bob-Omb cage, and to get Maple
Syrup in Bullet Bill Room

Mt. Rugged
 - Kooper or Parakarry needed to get Letter on ledge
 - Parakarry needed to reach Quake Hammer, to get to Bub-ulb, to reach Star Piece, and to reach entrance to Desert

Dry Dry Ruins
 - Bombette needed to open entrance to second sand-filled room (which also has a Star Piece and lets you reach a Ruins Key), to open entrance to long drop with the Super Block, and to open entrance to Diamond Stone room

Boo's Mansion
 - Bombette to open the entrance between the library with Boo's portrait and the chest room
 - Parakarry to reach the Boo's Portrait item

Gusty Gulch
 - Parakarry to cross the gap in the final scene

Tubba Blubba's Cast;e
 - Bombette to open the entrance to the room with three floorboards above the table with D-Down Jump
 - Parakarry to reach the Mega Rush badge
 - Bow or Lakilester to reach the chest in the rising-and-falling-spikes room
 - Bow to maybe to avoid the Sentinels and Invincible Tubba Blubba? (I don't know if it's possible to avoid all of the Sentinels without her)

Shy Guy's Toy Box
 - Kooper to reach a Shooting Star in Red Station
 - Bombette to break down the wall blocking off most of the right path of Red Station
 - Parakarry to reach a Star Piece on a building in Blue Station, to reach a Thunder Bolt in Blue Station, and to reach the Dictionary chest in Green Station
 - Bow to pass the wall on the conveyor belts in Green Station
 - Watt to open the entrance leading to General Guy

Whale
 - Watt to fight Fuzzipede

Jade Jungle
 - Watt to talk to a Yoshi Kid in the dark room
 - Sushie to reach a Bub-ulb + Star Piece + Letter in one area, to reach a Star Piece in another area, to reach Power Quake in another area, and to travel between almost every entrance

Mt. Lavalava
 - Bombette to break open an entrance in the escape-with-Misstar cutscene
 - Parakarry or Lakilester to cross the lavafall with the pushable blocks above it, to cross the lavafall in the room with Dizzy Stomp, and to cross the lavafall in the room with the Ultra Hammer

Flower Fields
 - Bombette to access the Mega Smash badge and lower the Sun Tower
 - Parakarry or Lakilester to cross the thorny gaps past the yellow gate
 - Sushie to cross the lake after saving Lily, and to reach the Bubble Berry tree
 - Lakilester to solve the puzzle with all the colored floors to ground pound

Shiver City
 - Sushie to collect the key in the lake

Shiver Mountain
 - Kooper to hit the ! Switch guarded by the Duplighost
 - Bombette to open the entrance to Madame Merlar

Shiver Palace
 - Kooper to open the path past the rotating wall room (the bad Duplighost mimics) and to hit the ! Switch leading to the Albino Dino room
 - Bombette to open both entrances behind the Blue Key door, to open the entrance to the Red Key, to open the entrance to Triple Dip, and to hit the ! Switch in the rotating wall room

Bowser's Castle
 - Kooper or Bombette to hit a ! Switch leading to a key
 - Bombette to open the entrance out of the prison, to open an entrance between the tops of the flooded rooms, and to hit the ! Switch leading to an Ultra Shroom
 - Parakarry to cross the platforms in the lava floor and to cross wide gaps in the underground dark rooms
 - Bow to pass through the lavafall
 - Sushie to cross the flooded rooms for the key
 - Lakilester to cross the lava floor