Porygon Z — every printing, every price, every gap.

Additional software was installed to make it a better Pokémon. It began acting oddly, however. Its programming was modified to enable work in alien dimensions. It did not work as planned. Its programming was modified to enable it to travel through alien dimensions. Seems there might have been an error... In order to create a more advanced Pokémon, an additional program was installed, but apparently it contained a defect that makes it move oddly. Its program was modified to facilitate extra-dimensional activities, but that led to noticeably strange behavior.