Badge

Badges are items used by Mario in Paper Mario, Mario & Luigi: Superstar Saga, Paper Mario: The Thousand-Year Door, and Mario & Luigi: Partners in Time. In all four games they are equipped as accessories, similar to the weapons, armors and accessories from Super Mario RPG: Legend of the Seven Stars, the main difference being that, while these items serve to raise Mario's stats, not all the badges raise Mario's stats. The badges instead have many different uses, from prolonging Mario's Spin Dash to changing the sound effects of Mario's hammer and jump attacks. Some badges also allow Mario to use special attacks with the hammer and shoes that use FP.

Each badge requires a certain amount of BP to be equipped, which means that Mario can't equip all the badges at the same time. The more useful a badge is the more BP it requires.

Badges can be found scattered in all the Mushroom Kingdom, but some particular badges can be only bought from Rowf in Toad Town and from Merlow in exchange for Star Pieces.

Paper Mario Series
Badges can be obtained in a multitude of ways in the Paper Mario series. Most badges provide a special attack for Mario and consume BP (Badge Points) when equipped. Total number of badges: 69.

Unused Badges of Paper Mario
In the game's coding, many badges can be found that are entirely unavailable except through hacking. A list of them can be viewed here.

Paper Mario: The Thousand-Year Door
Notes: Equipping more than one of the jump or hammer attack badges Mario has already obtained doubles FP requirements, but increases attack power by 1. When wearing both Double Dip badges, Mario can use Triple Dip for 8 FP. For more than one Charge badge, Mario or his partner gains an extra 3 attack power for 2 FP for the next turn. When both the W Emblem and L Emblem are equipped, Mario's clothes will change into Waluigi's clothes..

Total number of badges: 85.

* When using P-Down D-Up (P) the defense point added additionally decreases damage received from a defense-piercing attack by 1, whereas even Defend Plus doesn't protect against such an attack.

Unused Badges of Paper Mario: The Thousand-Year Door
There are also many badges that can be found only in the game's coding. A list of all these badges can be found here.

Mario & Luigi: Superstar Saga
In this game, badges do not provide new attacks. However, they do increase POW and BP, and sometimes have other special features. BP is not Badge Points, but Bros. Points, and serves a completely different function. Each brother can only wear one badge at a time. If a small number is shown in the last column, refer to the end of the table for that effect.

– No effect. 1 Increases counterattack power. 2 Increases POW in battle. 3 Recover 2 BP every turn. 4 Enemies will drop items more often. 5 Recover HP equal to 1/10 damage dealt with Hand attacks. 6 Increases frequency of Lucky hits. 7 Recover HP equal to 1/10 damage dealt with Jump attacks. 8 The more Mushrooms in your possession, the more damage your attacks will do. 9 Recover HP equal to 1/10 damage dealt with Hammer attacks. 10 Inflict twice as much damage on Spiny enemies with Jump attacks.

Mario & Luigi: Partners in Time
In the second installment, the setup is the same, except that badges only add special effects to each of the four brothers. Clothing increases and decreases all the stats in this game. If the Location is "Fawful's Bean 'N Badge", the price is in number of beans.

Trivia

 * Super Paper Mario eliminates the use of badges for there is no RPG style battling system. Although, there are two items that were previously badges in the past games: Power Plus and HP Plus; they retain their main purpose. Power Plus boosts the character's attack power by one and the HP Plus boosts the character's Heart Points by five. But with the badges they had to be equipped and could be unequipped. In the most recent game, once it is used, it's permanent. The Happy Flower, albeit distinctly different than its badge form, also appears in Super Paper Mario as an item.