Mahirap magsabi ng diretso unless tanungin mo si Jeff Untalan na naka-embed sa pic he he. Marami kasing paraan using AI tools nowadays.
Sa itsura ng resulting pic compared sa original, ang ginamit dyan (whether online service or offline applications) is similar to Stable Diffusion's multiple step Inpainting (animal ears, changing of background, changing of hairstyle, skin, props, cropping, etc., img2img upscaling and using the same Seed) with custom prompts - the hard way. Other similar AI generators use the same process kaya nakadepende na yan sa sequence of prompts, use of checkpoints, loras, upscalers, denoising and other settings/accessories on the app/s used to get a similar effect.
Ang pinakamadaling naisip ko ay nag-generate or naghanap siya ng pinakamalapit na pic ng ka-edad ng bata (with the same pose) na may hawak na pusa (o hayop) or nilagay na lang niya after that, at yon yung kanyang pinalitan ng mukha noong original image, and the rest is upscaling, denoising or tuning the face, etc. for the final result. The sequence may vary. Kita mo naman na iba na yung pusa sa result. Use your imagination while comparing pics he he.
I'm just giving an idea to start dahil kahit meron kang tool o website, you can't process correctly if you don't know what to do.
Sana may eksaktong makatulong sa'yo.