  The increasing number of transiting planets raises the possibility of finding
changes in their transit time, duration and depth that could be indicative of
further planets in the system. Experience from eclipsing binaries indeed shows
that such changes may be expected. A first obvious candidate to look for a
perturbing planet is GJ 436, which hosts a hot transiting Neptune-mass planet
in an eccentric orbit. Ribas et al. (2008) suggested that such eccentricity and
a possible change in the orbital inclination might be due to a perturbing small
planet in a close-in orbit. A radial velocity signal of a 5 M_earth planet
close to the 2:1 mean-motion resonance seemed to provide the perfect candidate.
Recent new radial velocities have deemed such signal spurious. Here we put all
the available information in context and we evaluate the possibility of a small
perturber to GJ 436 b to explain its eccentricity and possible inclination
change. In particular, we discuss the constraints provided by the transit time
variation data. We conclude that, given the current data, the close-in
perturber scenario still offers a plausible explanation to the observed orbital
and physical properties of GJ 436 b.
