  In spite of the vast literature on the subject of first order Electroweak
Phase Transitions (EWPTs), which can provide the necessary conditions for
generating the Baryon Asymmetry in the Universe, fermion-induced EWPTs still
remain a rather uncharted territory. In this paper, we consider a simple
fermionic extension of the Standard Model involving one $SU(2)_L$ doublet and
two $SU(2)_L$ singlet Vector-Like Leptons, strongly coupled to the Higgs boson
and with masses close to the TeV scale. We show how such a simple scenario can
give rise to a non-trivial thermal history of the Universe, involving strongly
first order multistep phase transitions occurring at temperatures close to the
electroweak scale. Finally, we investigate the distinct Gravitational Wave (GW)
signatures of these phase transitions at future space--based GW detectors, such
as LISA, DECIGO, and BBO, and briefly discuss the possible LHC signatures of
the Vector-Like Leptons.
