  Context: The accretion history of the Milky Way is still unknown, despite the
recent discovery of stellar systems that stand out in terms of their
energy-angular momentum space, such as Gaia-Enceladus-Sausage. In particular,
it is still unclear how these groups are linked and to what extent they are
well-mixed.
  Aims: We investigate the similarities and differences in the properties
between the prograde and retrograde (counter-rotating) stars and set those
results in context by using the properties of Gaia-Enceladus-Sausage,
Thamnos/Sequoia, and other suggested accreted populations.
  Methods: We used the stellar metallicities of the major large spectroscopic
surveys (APOGEE, Gaia-ESO, GALAH, LAMOST, RAVE, SEGUE) in combination with
astrometric and photometric data from Gaia's second data-release. We
investigated the presence of radial and vertical metallicity gradients as well
as the possible correlations between the azimuthal velocity, $v_\phi,$ and
metallicity, [M/H], as qualitative indicators of the presence of mixed
populations.
  Results: We find that a handful of super metal-rich stars exist on retrograde
orbits at various distances from the Galactic center and the Galactic plane. We
also find that the counter-rotating stars appear to be a well-mixed population,
exhibiting radial and vertical metallicity gradients on the order of $\sim$
-0.04 dex/kpc and -0.06 dex/kpc, respectively, with little (if any) variation
when different regions of the Galaxy are probed. The prograde stars show a
$v_\phi$-[M/H] relation that flattens -- and, perhaps, even reverses as a
function of distance from the plane. Retrograde samples selected to roughly
probe Thamnos and Gaia-Enceladus-Sausage appear to be different populations yet
they also appear to be quite linked, as they follow the same trend in terms of
the eccentricity versus metallicity space.
