  We consider field sets that do not form complete SU(5) multiplets, but
exactly preserve the one-loop MSSM prediction for $\alpha_3(M_Z)$ independently
of the value of their mass. Such fields can raise the unification scale in
different ways, through a delayed convergence of the gauge couplings, a fake
unified running below the GUT scale, or a postponed unification after a hoax
crossing at a lower scale. The $\alpha_3(M_Z)$ prediction is independent of the
mass of the new fields, while the GUT scale often is not, which allows to vary
the GUT scale. Such "magic" fields represent a useful tool in GUT model
building. For example, they can be used to fix gauge coupling unification in
certain two step breakings of the unified group, to suppress large KK
thresholds in models with extra dimensions, or they can be interpreted as
messengers of supersymmetry breaking in GMSB models.
