This paper reports on a Virtual Reality theater experiment named Il 'etait Xn fois, conducted by artists and computer scientists working in cognitive science. It offered the opportunity for knowledge and ideas exchange between these groups, highlighting the benefits of collaboration of this kind. Section 1 explains the link between enaction in cognitive science and virtual reality, and specifically the need to develop an autonomous entity which enhances presence in an artificial world. Section 2 argues that enactive artificial intelligence is able to produce such autonomy. This was demonstrated by the theatrical experiment,"Il 'etait Xn fois" (in English: 'Once upon Xn time'), explained in section 3. Its first public performance was in 2009, by the company D'er'ezo. The last section offers the view that enaction can form a common ground between the artistic and computer science areas.