  Kepler-78b is one of a growing sample of planets similar, in composition and
size, to the Earth. It was first detected with NASA's \emph{Kepler} spacecraft
and then characterised in more detail using radial velocity follow-up
observations. Not only is its size very similar to that of the Earth ($1.2
R_\oplus$), it also has a very similar density ($5.6$ g cm$^{-2}$). What makes
this planet particularly interesting is that it orbits its host star every
$8.5$ hours, giving it an orbital distance of only $0.0089$ au. What we
investigate here is whether or not such a planet could have been perturbed into
this orbit by an outer companion on an inclined orbit. In this scenario, the
outer perturber causes the inner orbit to undergo Kozai-Lidov cycles which, if
the periapse comes sufficiently close to the host star, can then lead to the
planet being tidally circularised into a close orbit. We find that this process
can indeed produce such very-close-in planets within the age of the host star
($\sim 600 - 900$ Myr), but it is more likely to find such ultra-short-period
planets around slightly older stars ($> 1$ Gyr). However, given the size of the
Kepler sample and the likely binarity, our results suggest that Kepler-78b may
indeed have been perturbed into its current orbit by an outer stellar
companion. The likelihood of this happening, however, is low enough that other
processes - such as planet-planet scattering - could also be responsible.
