I don't know if it addresses your question at all, but I see major errors.

The only thing that should be mortal is the RV you return. Everything else is being referenced.

The fourth argument of hv_store is documented to be an SV*. I don't see how what you have could even compile.

SV* get_data() {
  AV * results;
  I32 nr = 0;
  int n;
 
  results = newAV();
 
  for (n = 0; n <= nr; n++) {
    HV * rh = newHV();

    {
       SV * val = newSVpv("mouse", 0);
       hv_store(rh, "mickey", 6, val, 0);
    }

    {
       SV * val = newSVpv("kong", 0);
       hv_store(rh, "donkey", 6, val, 0);
    }
 
    av_push(results, newRV_noinc((SV*)rh));
  }
 
  return newRV_noinc((SV*)results);
}
[download]

Untested.

The usage of newRV is not documented, so I used newRV_noinc.

Your loop is completely useless, but I left it in since I figure you would eventually use it.