Octopodes use hemocyanin... use CRISPR to take that out, lenti vector to replace with hemoglobin, and you've got a super-octopus.

Now just apply MIRI's magic formula for making friendly superintelligence, and you've got your tame octopus. Great basis for a TV show in the genre of "Lassie", "Flipper", or "Skippy the Bush Kangaroo".

"Good on ya', Cthulipper!"

Octopuses have poisonous bites, of course.... some would see that as a bad quality in a pet.