The HD domain of ey has been replaced by the HD domain of eyg.
eye | ectopic, with Scer\GAL4dpp.blk1
As with overexpression of wild-type ey, expression of ey::eygEEEEGE.Scer\UAS, under the control of Scer\GAL4dpp.blk1, leads to the formation of ectopic eyes on appendages.