  We critically examine a number of theoretical uncertainties affecting the
MiniBooNE short-baseline neutrino oscillation experiment in an attempt to
better understand the observed excess of electron-like events. We re-examine
the impact of fake charged current quasi-elastic (CCQE) events, the background
due to neutral current $\pi^0$ production, and the single-photon background.
For all processes, we compare the predictions of different event generators
(GENIE, GiBUU, NUANCE, and NuWro) and, for GENIE, of different tunes. Where
MiniBooNE uses data-driven background predictions, we discuss the uncertainties
affecting the relation between the signal sample and the control sample. In the
case of the single-photon background, we emphasize the uncertainties in the
radiative branching ratios of heavy hadronic resonances. We find that not even
a combination of uncertainties in different channels adding up unfavorably (an
"Altarelli cocktail") appears to be sufficient to resolve the MiniBooNE
anomaly. We finally investigate how modified background predictions affect the
fit of a $3+1$ sterile neutrino scenario. We carefully account for full
four-flavor oscillations not only in the signal, but also in the background and
control samples. We emphasize that because of the strong correlation between
MiniBooNE's $\nu_e$ and $\nu_\mu$ samples, a sterile neutrino mixing only with
$\nu_\mu$ is sufficient to explain the anomaly, even though the well-known
tension with external constraints on $\nu_\mu$ disappearance persists.
