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.
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