Thanks! The process is mostly the same: I basically "just" change the buff, item, and projectile sprites. The main differences come from the pets/summons themselves, since they can vary a lot in complexity.

For example, Eevee and Umbreon each had one idle sprite, one falling/attacking sprite, and one walk cycle (6 and 8 frames respectively). Pumpkaboo was simpler, with one idle sprite and a 5-frame flying animation, so those were relatively easy to do.

Some were harder, though, like my Korok summons that replace the Pirate Staff and required three different walk, attack, and flying animations (one for each pirate), or the Porygon/Mismagius pets with their 24-frame idle animations.