It is too easy to duplicate characters in Pools of Darkness (and possibly the other Gold Box games) to the point where I have done it by accident.

Here is a comparison with some other early cRPGs:

Wizardry: Copy your character disk, rename and transfer the character from the copy to the original. Requires the deliberate action of copying the disk plus the time it takes to copy the disk.

Bard's Tale: Use the transfer utility to transfer the character from and to the same disk. You will be asked to rename the character. Alternatively, in 3 and some versions of 2, save the game with the character outside, rename the character in the Adventurer's Guild, reload the save (where the character still has the old name), and remove the character at the guild. Easier, but is still not something likely to happen by accident.

Pools of Darkness: Add the character to the party and then Remove that character. You will be asked if you want to overwrite the character. If you say No (a perfectly reasonable choice), you are prompted to enter a new name for the character (no option to back out) and the character has now been duplicated. This is so easy it can happen by accident, as it happened to me while experimenting.