Would you want to have an identical twin?

[Rain Man]

Not necessarily an evil twin or anything. Just an identical one.

Advantages:

1. Built-in pal of the same age throughout life.
2. You can see how clothing looks on you without a mirror.
3. You can score with each others' wives on moonless nights.
4. Easy to confuse authority figures seeking to blame you for offenses ranging from truancy to murder.
5. Easy to build your own nature vs. nurture experiments.
6. Possible secret language.

Disadvantages:

1. Generally creepy to know that there's another one of you running around.
2. 1/3 of time - called by right name, 1/3 of time - called by wrong name, 1/3 of time - called "the twins".
3. Probably get shafted on birthdays.
4. Possibly harder to get top secret clearances.
5. Possible frameups for murder if twin is indeed evil.
6. Probable splitting of the vote for "Most likely to succeed", "Best looking", "Most studious", etc., in high school.