  The brightest planetary nebulae achieve similar maximum luminosities, have
similar ratios of chemcial abundances, and apparently share similar kinematics
in all galaxies. These similarities, however, are not necessarily expected
theoretically and appear to hide important evolutionary differences. As
predicted theoretically, metallicity appears to affect nebular kinematics, if
subtly, and there is a clear variation with evolutionary stage. To the extent
that it can be investigated, the internal kinematics for galactic and
extragalactic planetary nebulae are similar. The extragalactic planetary
nebulae for which kinematic data exist, though, probably pertain to a small
range of progenitor masses, so there may still be much left to learn,
particularly concerning the kinematics of planetary nebulae that descend from
the more massive progenitors.
