I Built My Own Mini Pet in Codex

It’s been a while since I shared a proper build on Smart Alex. When I started making AI videos, I wanted to help people see what they could create. But the feedback was often that there was already too much information to take in.

So I’m taking a more hands-on approach: build something, have fun with it, and share the process. Hopefully, watching an idea become something real makes it easier for you to start your own experiment.

For this one, I built a custom mini pet in Codex: a little animated desktop companion with an anime-inspired mecha design and transformations that change with what it’s doing.

Watch the build

The full video shows the character taking shape, the animation previews, and the finished companion in action.

Watch “I Built My Own Mini Pet in Codex!” on YouTube ↗

Start with a character you actually like

One of my favourite parts of building a pet is that you can customise its design. It gives you a reason to think about how something should look and behave, rather than just asking an AI tool to make whatever it wants.

I went for a transforming mecha character. I wanted the companion to have different suits and reactions, so running, jumping, reviewing code, and looking around could each have their own feel.

You could start much simpler: a sleepy robot, a tiny dragon, or a curious little creature. Pick a design you’ll enjoy seeing on your desktop, then decide how it should respond to a few activities.

The animations are where it comes to life

A good character image is a start. Seeing it wave, read, jump, and move is what makes it feel like a companion.

In the video, the workflow generates the artwork, puts the supporting files together, and uses a Python script to render the animation previews. Those previews let me see the character’s movements before selecting the finished pet.

I also steered the build along the way. If an animation needed a different look or a transformation wasn’t quite what I wanted, I could give it more direction. That back-and-forth is part of the fun: generate something, look at it, and make a specific change.

If you’re trying this yourself, I’d start with a few clear actions. Get the character looking consistent while it’s idle, waving, and moving, then add more ambitious transformations.

What I learned about model choice

I hit a Codex usage limit during the build, which gave me a reason to rethink which model I was using for each part of the work.

In this session, I found a lighter model was enough for much of the iteration and used less of my allowance. That was useful when I wanted to keep adjusting the pet rather than spend everything on the first pass.

The practical lesson for me is to choose a model that fits the job. Small adjustments don’t always need the most capable option available. Image generation is its own part of the workflow, though, so the tools needed to create the artwork still matter.

I also explored Ollama as an alternative for continuing development with a local model. That’s something I’ve covered on the channel before. For this pet, I’d still keep the image-generation work with a tool that supports it; moving to a local coding model doesn’t automatically replace that step.

Don’t forget to select the finished pet

Once the files and previews were ready, there was one more step: go into the pet picker and select the new character.

Then I could see the result properly: jumping, changing appearance, and bringing up the chat controls. After all the previews and adjustments, having the little companion there on the desktop was a satisfying finish.

If you want to try the desktop creation flow, the official pet guide explains how to open Settings → Pets → Create pet, describe your character, and refresh the picker when the build is finished. The guide also explains where custom pets are stored and how pet behaviour differs between interfaces.

A prompt to start your own experiment

Here’s a starter prompt you can adapt. This is a suggested starting point, rather than the exact prompt from my video:

Create an original mini pet for my desktop: a friendly transforming robot with a clear silhouette. Give it consistent idle, waving, reading, running, and jumping animations. Keep it recognisable at a small size, preview the movements, and help me select the finished pet.

Swap the robot for your own idea. Once you have a preview, try asking for one specific improvement at a time.

Build something because it’s fun

This was a small project, but it got me building again. I had a character I wanted to make, a result I could see, and plenty of little decisions to work through along the way.

You don’t need a huge app idea to get started. Pick something that makes you curious and see what you can build with it.

I’ll keep sharing these experiments on Smart Alex. Come build along with me on YouTube ↗