From Bulbapedia, the community-driven Pokémon encyclopedia.
The Ditto egg group is one of the sixteen egg groups. It is the only group which has only one member.
Being that there is only one Pokémon, Pokémon in the Ditto group are all shapeless, purple blobs. However, they have the ability to breed with every member of every other egg group, but the "No eggs" egg group (In exception of Nidorina and Nidoqueen)
Only in this egg group
In this and another egg group
- Pokémon in the Ditto group can breed with any Pokémon from any egg group, excluding the No eggs Egg Group. Ditto also cannot breed with members of its own group.
- The exception to the above rule is that Pokémon in the Ditto group can also breed with Nidorina and Nidoqueen, both of which are part of the No eggs group.