  A significant fraction of planetary nebulae (PNe) and proto-planetary nebulae
(PPNe) exhibit aspherical, axisymmetric structures, many of which are highly
collimated. The origin of these structures is not entirely understood, however
recent evidence suggests that many observed PNe harbor binary systems, which
may play a role in their shaping. In an effort to understand how binaries may
produce such asymmetries, we study the effect of low-mass (< 0.3 M_sun)
companions (planets, brown dwarfs and low-mass main sequence stars) embedded
into the envelope of a 3.0 M_sun star during three epochs of its evolution (Red
Giant Branch, Asymptotic Giant Branch (AGB), interpulse AGB). We find that
common envelope evolution can lead to three qualitatively different
consequences: (i) direct ejection of envelope material resulting in a
predominately equatorial outflow, (ii) spin-up of the envelope resulting in the
possibility of powering an explosive dynamo driven jet and (iii) tidal
shredding of the companion into a disc which facilitates a disc driven jet. We
study how these features depend on the secondary's mass and discuss
observational consequences.
