In theatre/film non-traditional casting can refer to casting without regard to gender (such as Cate Blanchett playing Bob Dylan in I'm Not There). It can also refer to switching races/species to either make a statement or to simply use color-blind casting. District 9's use of the alien Prawns to serve as a symbolic representation of South Africa's apartheid era is a good example of casting against species for meaning. Night of the Living Dead's use of a black lead in a traditional "white" hero role--GREAT casting idea!--is a prime example of using a different race to make a statement (the actor was great in the role anyway so he should have been cast). Using black actors in a Shakespeare play would just be color-blind casting in most cases.
Duo and Duet can use non-traditional casting as well in certain instances. If you find an amazing piece but it does not meet the specifications you require do not label it as rubbish immediately. Ask yourself: can non-traditional casting work with this script? Race hardly is an issue unless you are doing a race related work. Then you should adhere to the author's intent or you most likely will diminish the message's impact. Gender however is the casting decision to really think about.
Does this Duo or Duet piece really require you and your partner to stick with the genders assigned by the author? If gender is central to the plot, character relationship type, or many of the gags then switching genders is not in your best interest. However, if your Duo or Duet's gender assignments mean nothing, or only a couple of jokes that can be cut are related to gender, some editing can make this piece doable by whatever genders you wish. It could even be fun casting a female in the male role and a male in the female role (such as with a business partnership cast a girl as the executive, a male as the secretary).
If you are planning on switching genders be sure your league allows for such changes. I competed in Illinois where up to 15% of the material did not have to be original content. Therefore, when my Duet Acting partner and I took a comedic piece intended for two males and changed one of the characters name's to the female equivalent, we were perfectly within our right and piece legal. We were somewhat successful as well placing in a few tournaments throughout the season--not bad for this being both of ours secondary event. So, using non-traditional casting in Duo or Duet can either be a decision that goes unnoticed or which causes a commotion for testing the audience's ideas about race/gender.
What do you Duo and Duet people think? Have you, or would you, cast outside the box?