a small question

what happens when you breed a themed pet with a non-themed one? a themed or non-themed? half themed?

Crossing a themed with a non-themed will result in a non-themed. Crossing a theme with a different theme (with one special exception) will also give you a non-themed. The only exception (at least for now) is crossing a first generation (gold star, purple name - also often called 'tagged') Dawnbreaker Aeridini with a first generation Frostkeeper Aeridini. This gives a Mistwarden Aeridini, and this was the only method to get Mistwardens (therefore there are no tagged/gold star Mistwarden aeris. They are a purely purebred theme). Breeding purebred (blue star, blue name) Dawnbreakers with purebred Frostkeepers will not give you a Mistwarden, though. This will result in another non-themed offspring instead.

thank you!