1998, May 28th:

Petz 3 press releases mention that Pigz were originally planned as Petz 3 DLC, as part of a "species module" system of expansion packs and dlc. (Source: Archived Petz 3 Pre-release Press Release.)

Dogz 3 and Catz 3 are easily expandable and new modules can be downloaded from the Petz Web site. These new modules include:
- Voice Recognition Technology (“Come here, Fido!”)
- New species, such as pigz and ferretz
- A Petz mailbox that actually “fetches” your e-mail
- Additional breedz, play scenes, accessories and clothing

1998, August:

The Dogz 3 CD book shows a prototype image of a Pig, as an example of the downloads available on Petz.com:

1999, February:

A prototype pigz was accidentally released on the Petz.com Adoption Center. Its name was Wilbur. (Source: Silver's Petz Place.)

Although the mystery as to where the other breeds in the PF.Magic adoption center came from was figured out, I still believe the pigz I found to be real (read why on my message forum under "general discussion"). Because of that and because many people enjoy the pigz, you can still play with a Pigz.

This incident is also mentioned in the readme text file for the petz 3 version of Carolyn's pig-hogz breedfile: the pink variation in the breed is apparently modeled directly off of this prototype "Wilbur" petfile:

You have five choices of pig types in this breed:

1) the Pink P.F.Magic breed cloned from "Wilbur", a pet who was once accidentally uploaded to their Adoption Centre back in the early days of Petz 3. This is an almost identical clone.

1999, September:

Dogz 4 came out, with Pig.dog included as a breed.

2000:

Carolyn Horn creates the first "breedable pig" OW. (source: "last modified" date on Carolyn's pig OW.) Essentially, it functions by putting pig lnz into a bulldog.dog breedfile chassis, giving the pigz access to dogz mating behavioral data. It also changes the pig.dog breedfile's ID number to FFFFF, allowing already-adopted pigz (who have nulled-out looks chromosomes) to access breedfile lnz for genetic purposes.

2000:

Emerald Gate Pigz, the first pigz-centric petz site, is founded. Unfortunately, only scraps of it are archived. Whatever wisdom it held on the matters of petz 3's Wilbur, carolyn's pig-hogs, and petz 4's pigz, is sadly now lost forever...