Peaked sources and narrow-line Seyfert 1s: a love story
  The first similarities between peaked sources (PS) and narrow-line Seyfert 1
(NLS1) galaxies were noticed already twenty years ago. Nowadays, it is known
that several sources can share both classifications, and that part of the
parent population of $\gamma$-ray emitting NLS1s could be hiding among PS. In
this brief review, we describe how and why this orientation-based unification
was developed. We also show how the recent discovery of absorbed radio jets in
NLS1s, basically invisible at frequencies below 10 GHz, could impact our
knowledge of PS and, in particular, render the widely used radio-loudness
parameter obsolete.
