An example of a T-Shirt.
T-Shirts are a decal on the front torso of a ROBLOXian that show up in game and on the avatars picture. Most of the time T-Shirts are made to run ads, or advertise groups, also to get donations and VIP abilities. These are alike to the shirts, just a decal only on the player's chest. Even though everyone, including NBC can make them, only Builders Club members have the ability to sell them.
History
Before March 2007, T-Shirts could not be created by users. Only ROBLOX could sell T-shirts, and players who contributed to the community (such as MrDoomBringer, who helped maintain the wiki) were rewarded with character customization, such as body part color and a decal on the torso, which would become T-Shirts.
The first players to customize their character
On March 2007, an update was released that allowed players to modify their character, and they could create their own T-Shirts.
On April 2008, Shirts and Pants were released, which cover more of the character than T-Shirts can. For this reason, T-Shirts have become less popular for cosmetic use than shirts or pants.
Purposes
T-shirts are not as popular for aesthetics as they were in 2007 and early 2008, but they remain popular for serving other purposes.
Advertisement Support
A few well known players run comical ads through T-Shirts, like SadietheKisser.
Groups
Some T-shirts include a link to the group, so that they are advertised,as Roblox previously did not let groups advertise themselves directly. In February 2011, Roblox allowed groups to be advertised directly, so groups do not need to use t-shirts to advertise.
Donations
Some Builders Club members use T-Shirts to get donations for hats or gear, but this usually isn't the best effective way to get money.
VIP T-Shirts
VIP T-Shirts are a good way to get money if you have a popular place, mostly used to get into special rooms in special games, like extra money in tycoons, or extra characters in Class games or get gear that the other players don't get. Other users use the new Game Pass feature, but most prefer T-Shirts as creating a Game Pass makes no change but powers and T-Shirts are free like gamepasses but you can wear them.
Drawings
Some members offer a certain amount of money to have users be drawn on a T-Shirt made especially for them.
Exploitation
People can exploit the use of t-shirts by selling a t-shirt for 10 tickets, creating accounts and buying it. This gives themselves money from each account. Users use this way to earn 10 tickets per new account. This no longer works as tickets were removed in April 2016.