its not a hybrid, but figured this is probably the best forum for it...?

most agree the Gymnocalycium chimera is with a Myrtillocactus geometrizans....though there are some that think it is with a Hylocereus (even though the spines on the chimera are way off for hylocereus, and mutated for Myrtillocactus).

this picture should end any question what the green species is

No mistaking what that is.

Kada,

you are right, halfway. Nobody assumes a blue Myrtillocactus behind this green surface.
But there is also a Chimera between Hylocereus and Gymnocalycium.
The Hylocalycium chimera is published in detail in Teratopia from Gordon Rowley p. 98/99
It shows sometimes aerial roots - which no Myrtillo has.

looks awsome!
did you do that??

Chef