Hi there, the Series 1 foil packs (squirrel, cat, turtle) were what got me back into Lego a few months ago (as an adult, I mean -- prior to that I was playing with Legos as a child in the 80s). Each one took me about 5 minutes to build, and I was immediately hooked on Lego Friends and started buying the larger boxed sets. As mentioned by another poster, Lego provides instructions on their website on how to construct alternate versions of each animal's habitat, as well as a combined super-habitat that incorporates *all three* Series 1 sets -- you know, so that the squirrel, cat, and turtle can live together in harmony (I'm downloading these instructions in case they disappear from the site in the future!). Series 2 (poodle, hedgehog, bunny) just came out recently, and from the Lego Store website it looks like Series 1 will be retiring soon. From the Brickset website, it looks like a Series 3 (fawn, parrot, puppy) will come out this year as well. I'm definitely collecting all of them, but that's me--a rabid fan of anything Lego Friends.
To answer the questions above as to why these animal foil packs do not include minifigures, here's my insight: a big part of the Lego Friends collection is animals, specifically the caring for animals. I'm hoping they'll move on to other interest areas in the future (Hobbies! What about other hobbies?? Other stores to add to village??). Horses are big (Riding Camp, Emma's trailer, Olivia's Newborn Foal, Heartlake Stables). As well as dogs (Heartlake Dog Show, Pet Grooming Salon, Mia's Puppy House, Heartlake Vet). And undomesticated critters as well (The hedgehog shows up in more than one set and seems to have its own fan base, and I think I have at least 3 different rabbits by now). Oh and cats. There are sooo many cats.
These foil packs seem to enhance the existing boxed sets -- they add to the environment, the story line, the play value. The Series 1 kitty tower and scratching post would go great in Olivia's House. The poodle could visit the Pet Grooming Salon or compete in the Dog Show. And of course the bunnies could have their own enclave by now. Because they enhance larger sets, it would seem redundant to have a minifigure go with each one. As it is, I feel like there are too many variations of each of the 5 characters already. Does there need to be a version of Olivia for her house as well as her treehouse?
Anyway, hope this helps!