When you get an 'A' rank in the indicated challenege the corresponding Massage Parlor item will become available.

Unlock Bone Fangs:
Get an 'A' rank on the Koopa Corps challenge.

Unlock Furry Band:
Get an 'A' rank on the Bob-omb challenge.

Unlock Heroic Ring:
Get an 'A' rank on the Magikoopa challenge.

Unlock Treasure Ring:
Get an 'A' rank on the Goomba Storm challenge.

When you get an 'A' rank in the following challenges the corresponding Cholesteroad item will become available.

Unlock Advice Patch:
Get 'A' rank in Spin Pipe

Unlock Bro Socks:
Get 'A' rank in Yoo Who Cannon

Unlock Challenge Medal:
Get 'A' rank in Green Shell

Unlock Daredevil Boots:
Get 'A' rank in Jump Helmet

Unlock Dizzy Boots:
Get 'A' rank in Super Bouncer

Unlock Master Wear:
Get 'A' rank in ALL challenges

Unlock Siphon Gloves:
Get 'A' rank in Magic Window

To view this ending you must beat the game with Mario, Luigi, and Bowser ALL having reached at least Level 40.