  We present a novel method to detect variable astrophysical objects and
transient phenomena using anomalous excess scatter in repeated measurements
from public catalogs of Gaia DR2 and Zwicky Transient Facility (ZTF) DR3
photometry. We first provide a generalized, all-sky proxy for variability using
only Gaia DR2 photometry, calibrated to white dwarf stars. To ensure more
robust candidate detection, we further employ a method combining Gaia with ZTF
photometry and alerts. To demonstrate the efficacy, we apply this latter
technique to a sample of roughly $12,100$ white dwarfs within 200 pc centered
on the ZZ Ceti instability strip, where hydrogen-atmosphere white dwarfs are
known to pulsate. Through inspecting the top $1\%$ samples ranked by these
methods, we demonstrate that both the Gaia-only and ZTF-informed techniques are
highly effective at identifying known and new variable white dwarfs, which we
verify using follow-up, high-speed photometry. We confirm variability in all 33
out of 33 ($100\%$) observed white dwarfs within our top $1\%$ highest-ranked
candidates, both inside and outside the ZZ Ceti instability strip. In addition
to dozens of new pulsating white dwarfs, we also identify five white dwarfs
highly likely to show transiting planetary debris; if confirmed, these systems
would more than triple the number of white dwarfs known to host transiting
debris.
