  We discuss possible non-standard contributions to the top-quark width,
particularly the virtual effects on the standard decay $t\rightarrow W^+\,b$
within the context of the MSSM. We also place a renewed emphasis on the
unconventional mode $t\rightarrow H^+\,b$ in the light of recent analyses of
$Z$-boson observables. It turns out that in the region of parameter space
highlighted by $Z$-boson physics, the charged Higgs mode should exhibite an
appreciable branching fraction as compared to the standard decay of the top
quark. Remarkably enough, the corresponding quantum effects in this region are
also rather large, slowly decoupling, and most likely resolvable in the next
generation of experiments at Tevatron and at LHC.
