  We analyze the cosmological signatures visible to an observer in a Coleman-de
Luccia bubble when another such bubble collides with it. We use a gluing
procedure to generalize the results of Freivogel, Horowitz, and Shenker to the
case of a general cosmological constant in each bubble and study the resulting
spacetimes. The collision breaks the isotropy and homogeneity of the bubble
universe and provides a cosmological "axis of evil" which can affect the cosmic
microwave background in several unique and potentially detectable ways. Unlike
more conventional perturbations to the inflationary initial state, these
signatures can survive even relatively long periods of inflation. In addition,
we find that for a given collision the observers in the bubble with smaller
cosmological constant are safest from collisions with domain walls, possibly
providing another anthropic selection principle for small positive vacuum
energy.
