An excited superdeformed (SD) band in 150 Gd is associated with a two-particle-two-hole proton excitation and provides the first evidence for collective proton pair excitations in a SD nucleus. This band is seen to exhibit a discontinuity in the γ-ray transition energies (backbending), which is interpreted as a band crossing associated with the alignment of a pair of N=6 protons. There is further evidence that this excited SD band decays into the yrast SD band.