  Tadpole galaxies are metal-poor dwarfs with typically one dominant
star-forming region, giving them a head-tail structure when inclined. A
metallicity drop in the head suggests that gas accretion with even lower
metallicity stimulated the star formation. Here we present multiband HST WFC3
and ACS images of four nearby (<25 Mpc) tadpoles, SBS0, SBS1, Kiso 3867, and
UM461, selected for their clear metallicity drops shown in previous
spectroscopic studies. Properties of the star complexes and compact clusters
are measured. Each galaxy contains from 3 to 10 young stellar complexes with
10^3-10^5 Msun of stars ~3-10 Myr old. Between the complexes, the disk has a
typical age of ~3 Gyr. Numerous star clusters cover the galaxies, both inside
and outside the complexes. The combined cluster mass function, made by
normalizing the masses and counts before stacking, is a power law with a slope
of -1.12+-0.14 on a log-log plot and the combined distribution function of
cluster lifetime decays with age as t^{-0.65+-0.24}. A comparison between the
summed theoretical Lyman continuum (LyC) emission from all the clusters, given
their masses and ages, is comparable to or exceeds the LyC needed to excite the
observed Halpha in some galaxies, suggesting LyC absorption by dust or
undetected gas in the halo, or perhaps galaxy escape.
