  In this paper we describe a project we initiated to investigate individual
pixels in the downloaded Kepler apertures in order to find objects in the
background of the main targets with variable brightness. In the first paper of
this series we discovered and investigated 547 short-period eclipsing binaries
(Bienias et al. 2021). Here we present the independent discovery of 26 new RR
Lyrae stars in the Kepler background pixels obtained during the primary
mission, and provide continuous and precise photometry for these objects.
Twenty-one of these stars were already noted by Gaia or the Pan-STARRS survey.
This new population of dominantly faint and distant RR Lyrae stars increases by
50% and complements nicely the 52 already known main target RR Lyrae stars in
the original Kepler field. Despite their faintness, the four-year
quasi-uninterrupted light curves of these stars allow an unprecedented view of
these faint halo objects. We present an analysis of the light curves of the new
RR Lyrae sample, verify their classification using Fourier parameters, and
discuss the properties of these newly found pulsating variable stars. Most
notably, this is the first time that such faint RR Lyrae stars have been
investigated with the help of a photometric data set with outstanding cadence
and precision. Interestingly, these objects share the properties of their
brighter siblings in terms of sub-class characteristics, additional mode
content, and modulation occurrence rates.
