They are actually introduced in Paper Mario:the Thousand year door,with Rising Star,B-list Star,A-list Star,and Superstar.
The preceding unsigned comment was added by Yoshiyoshiyoshi (talk).

Good job 3X Yoshi, but this article pertains to ML:BiS only. I suppose it would be fair to link to the PM:TTYD article though.--Knife (talk) 20:51, 25 April 2011 (EDT)

Bonuses

Can anyone confirm if the bonuses affect both Bros.? (Besides Gear Slot and Badge effect Slot)