  We present here the general transformation that leaves unchanged the form of
the field equations for perfect fluid cosmologies in the DGP braneworld model.
Specifically, a prescription for relating exact solutions with different
equations of state is provided, and the symmetries found can be used as
algorithms for generating new cosmological models from previously known ones.
We also present, implicitly, the first known exact DGP perfect fluid spacetime.
A particular case of the general transformation is used to illustrate the
crucial role played both by the number of scalar fields and the extra
dimensional effects in the occurrence of inflation. In particular, we see that
assisted inflation does not proceed at all times for one of the two possible
ways in which the brane can be embedded into the bulk.
