  New family dependent fermionic interactions have been conjectured in several
extensions of the Standard Model that range from Supersymmetry to composite
theory up to flavor interactions. Strong constraints on these theoretical
scenarios can be derived from light fermion phenomenology and from B-mesons
studies. Corresponding constrains on the top quark sector are, on the other
hand, rather week. Tevatron data, on top quark pair production and decay in
dilepton channel, may suggest some deviation from the Standard Model
expectations. Such a deviation can be successfully re-interpreted in terms of
an exotic top decay that can arise in several theories beyond the Standard
Model. Further investigations at present and future colliders will provide
crucial tests on the models under discussion.
