Some players have reported issues with adding certain critters to their Collection panel. Despite feeding them food they love multiple times, they are not added to the collection and made available to follow the player.
We are continuing to keep an eye on this topic, but after investigation, it appears that the previously reported issue involving critters has been successfully resolved.
If you have fed a critter and believe that they should be added to your collection as an animal companion, it's important to consider the following:

1. Different critters require a different number of feedings of the food they love to become an animal companion -- it's not the same number for all critters.
2. Only the first feeding of the day for that critter counts towards the above total. If you look at the bottom-right side of the feeding screen, an icon will appear if you have already fed a given critter that day.
3. If you previously encountered issues with a given critter before the December 6 update (Missions in Uncharted Space), you will need to successfully feed them something they love one more time following the December update to add them as an animal companion.