  Temporary domain walls are produced during the bifurcation era of
multi-stream inflation. The observational effects from such a domain wall to
spectator field perturbations are calculated, and we expect the inflationary
perturbations share similarities with the case of spectator field. A domain
wall induces a preferred direction in the sky, affecting the angular
distribution of perturbations. A correlated suppression of multipoles together
with an alignment of multipole moments on the preferred direction are
generated. Other observational aspects of multi-stream inflation, including
hemispherical asymmetry and cold spot are also briefly reviewed.
