  Focusing on the twist angle for the minimal commensurate structure, we
perform nonperturbative calculations of electron dynamics in the twisted
bilayer graphene (TBG) under intense laser fields. We show that the TBG
exhibits enriched high-harmonic generation that cannot occur in monolayer or
conventional bilayers. We elucidate the mechanism of these nonlinear responses
by analyzing dynamical symmetries, momentum-resolved dynamics, and roles of
interlayer coupling. Our results imply nonlinear "optotwistronics," or
controlling optical properties of layered materials by artificial twists.
