  Many fascinating properties discovered in graphene and transition metal
dichalcogenide (TMD) moir\'e superlattices originate from flat bands and
enhanced many-body effects. Here, we discover new many-electron excited states
in TMD homobilayers. As optical resonances evolve with twist angle and doping
in MoSe$_2$ bilayers, a unique type of ``charge-transfer" trions is observed
when gradual changes in atomic alignment between the layers occur. In real
space, the optically excited electron-hole pair mostly resides in a different
site from the doped hole in a moir\'e supercell. In momentum space, the
electron-hole pair forms in the single-particle-band $K$-valley, while the hole
occupies the $\Gamma$-valley. The rich internal structure of this trion
resonance arises from the ultra-flatness of the first valence band and the
distinct influence of moir\'e potential modulation on holes and excitons. Our
findings open new routes to realizing photon-spin transduction or implementing
moir\'e quantum simulators with independently tunable fermion and boson
densities.
