In the annals of weird science: one team has figured out how to reshape the heads of worms. Specifically, "worms with the heads and brains of other species."
Normally, G. dorotocephala sports a pointy head with two elongated, earlike projections (called auricles) next to the eyes. After treatment, some of the worms developed their normal heads, while others grew rounded heads like those of S. mediterranea; heads with thick necks and pointy, catlike "ears" like those of P. felina; or triangular heads like those of D. japonica.
But don't worry, if you're concerned about species purity. "The changes are temporary for the worms, whose heads begin to revert back to their original shapes in weeks."
(thanks to Todd Bryant)