Guest

A guest is a special user for players wishing to not use a ROBLOX account. Guests are known as "The True Testers of ROBLOX" by the administrators. Either way, a guest is a user playing ROBLOX without an account. When a player hovers the mouse over a guest image when viewing game servers, the name will appear as "A Friendly Guest".

Many users create fake guest accounts (eg. Guest123, Guest_8164, etc.) and dress like guests. However, many people can identify if they are a guest or not, because users cannot leave spaces in their username. They can also be recognized since guest names do not have underscores, and all guests have one to four digits in their username (e.g. Guest 666)

From mid-2017 onward, playing as a guest is limited; meaning that after a certain about of plays or a time limit runs out, you'll have to create an account to continue playing Roblox, this was likely added to decrease the amount of people trying to play as a guest, in order to try to break the rules. They will get banned.

Guests were introduced on September 26, 2008.

Functionality
If a player joins a game but does not register or sign in, they are labeled as a guest by default. The guest's avatar is a placeholder for players interested in a game and want to play it before creating an account. The placeholders are BillyBloxxer, BettyBloxxer and DefaultGuest. When guests play games that save data (like money), they will lose all their data when they leave.

ROBLOX stores a cookie on the user's computer that keeps their ID. Cookie editors are able to change a guest's ID number by changing the UserID in Guest Data.

From 2008 to 2014, guests were able to speak by using the proper Super Safe Chat words. With the removal of Super Safe Chat they aren't able to speak or hear, which means guests are unable to communicate with others, and they have to create an account to chat. Recently, they have been given the ability to see text chat, but still can't chat.

It is possible for scripts to ban all players and not guests from a game. However, this violates the terms and conditions, because it makes some players believe that ROBLOX is a bugged game.

ROBLOX added trial play for guests, which limits them to 10 plays. When it ends, they have to make a ROBLOX account or they can no longer play ROBLOX.

Appearances
When Guests were first introduced in 2008, they appeared in the stereotypical "noob" colors of yellow head and arms, blue torso, and green-yellow legs. Later, Guests would be given the same appearance as the "ROBLOX" account, including hats, allowing Guests to technically "try" hats.

After that, there were gender options allowing Guests to appear as a "BillyBloxxer" or a "BettyBloxxer" They had very similar appearances to the user ROBLOX, but had different hats depending on the gender chosen. Billy Bloxxer wore the Red Roblox Cap, while BettyBloxxer wore the Pinktastic Hair. The DefaultGuest doesn't have an accessory; merely black limbs and a grey torso. On July 12, 2016, the appearances of the guests were modified for the first time. The male guest (BillyBloxxer) now wears the ROBLOX Jacket, the Black Jeans, and the True Blue Hair. The female guest is similar to the male guest except with the Lavender Updo Hair, which looks similar to the Chestnut Bun, but a different colour. The other male guest (DefaultGuest) is still similar except that it wears the ROBLOX Jacket and The Black Jeans. On September 13, 2016, guests began to wear the Robloxian 2.0 package and the ROBLOX 'R' Baseball Cap. Sixteen days later, the R15 body was applied to guests. After ROBLOX introduced a new logo, the guest's shirt changed to the new ROBLOX Logo Jacket on January 16, 2017 (six days after the logo began usage).

Gender
With the addition of new updates, both new users and guests can pick a gender for their character. Users can choose the male guest, which wears the ROBLOX Jacket, the Black Jeans, and the True Blue Hair. Users can also choose to be the female guest, which is the same as the male guest except it wears the Lavender Updo Hair. If playing without choosing your gender or playing on mobile, users will be loaded as a genderless guest (DefaultGuest). All guests that join a game in the iOS/Android version of ROBLOX will wear a ROBLOX jacket and jeans, the 2.0 body, and the ROBLOX 'R' Baseball Cap due to not being able to choose if you want to be a male or female guest in the iOS/Android version.

Criticism
Since many guests are new to ROBLOX, many will carry out activities that users find annoying, such as deleting people's creations, trolling, constantly following users around until they leave the server, or causing their team to lose.

Another issue with Guests is anonymity, allowing established user to perform the actions stated above without their name being known.

Guests cannot communicate with other players, though some games had guest talk scripts that allowed guests to communicate. Since then, they've been able to see text chat but still cannot talk without scripts.

There have been various petitions on ROBLOX to remove Guests, but Telamon clearly stated that guests are not going to be removed.

Blog Post
You can read the blog post of ROBLOX introducing the Guest feature in 2008 by clicking here.