As you can see, everything is relatively calm and ordered until Woof was introduced at Series 4.x. Until that time, Puppy Linux is a traditional, single distribution like others.
By the completion of 4.x series at version 4.3, however, there was an explosion and Puppy Linux become a family of distributions with multiple official Puppies at the same time.
At the end of Puppy Linux 4.3, Puppy Linux was split into multiple distributions (but still sharing the same principles, built using the same set of tools, and provide consistent features between all of them).
Lucid Puppy - a Puppy based on Ubuntu Lucid Lynx. The current version is Tahrpup, which is based on Ubuntu Trusty Tahr.
Slacko Puppy - a Slackaware-based Puppy. Originally it was built from Slackware 13.37; current version is uses Slackawre 14.1 as its base.
Racy and Wary - the traditional self-compiled T2-based Puppy.
Quirky - an experimental release of Puppy, which later was forked and made into its own distribution, independent of Puppy Linux.
In addition to the “official” puppies, there are also a multitude of unofficial Puppies, built by Puppy enthusiasts. Usually (but not always) made as a remaster, they fill the niche of almost every need. They are usually called as “puplets”.
They are as much a member of Puppy Linux family as the official releases themselves.
Here are some of the more notable puplets, in no particular order:
Macpup - a puplet by runtt21 which takes its design inspiration from Mac OSX™. Its main feature is that it uses the Enlightenment Desktop Environment.
Saluki - this one is by jemima and its standout feature is the XFCE desktop environment and “under the hood” innovations such as an ‘a-drive’ sfs which gets loaded at first boot. jemima is also famous for the puppeee and fluppy puplets - hardware specific puplets targeting the Asus EEE pc.
LightHouse Pup - a comprehensive puplet designed to be extended with specialised sfs packages for KDE, XFCE and other large programs. First developed by tazoc and later taken up by Dry Falls.
NOP (No Office Pup) - produced by gray featuring the removal of office apps and the addition of the XFCE Desktop Environment.
214X - an extension to the famous Puppy 2.1.4 with upgraded glibc, kernel and other updated software. Produced by ttuuxxx who has many more puplets!
Dpup Exprimo - a woof built puppy from the ground up by pemasu. This is a very well liked puplet even to this day. It has binary compatibility with Debian Squeeze. This could well have been an “official” Puppy!
This is by no means an exhaustive list. If running or even making a puplet is in your interest you should browse ally’s collection or vist the puplets area of the Puppy Linux Discussion Forum.
These are not considered Puppy Linux per se, but they own their existence to Puppy Linux in one way or another.
Quirky → Originally created by Barry Kauler as a test-bed for crazy and quirky ideas (hence its name) before integrating them to the main Puppy Linux.
When Barry stepped down, he handed over Puppy Linux to the community but kept Quirky to himself; and Quirky became a separate distribution separate from Puppy Linux. Although it feels very Puppy Linux-like due to its heritage, Barry himself said many times that Quirky is not Puppy and don’t expect it to behave and work like Puppy.
Even as a separate distribution, it still retains its purpose as a test-bed for various ideas. Maintained by Barry Kauler himself.
Woof-CE → Woof-CE is not a Puppy Linux distribution. It is actually a build system used to build various Puppy Linux distributions. It is listed here because it is also an offshot of Barry’s original Puppy Linux development.
Debian Dog → Adaptation of Debian Live-CD to make it behave like Puppy Linux. Originally started by forum member sickgut as a proof that any normal distribution can be molded to behave like Puppy Linux; it was later renamed to Debian Dog by Toni (aka saintless) and now managed by fredx181, its current maintainer.
Fatdog → Forked from Puppy Linux 4.0. Fatdog is notable in being the first Puppy-Linux like distribution that went fully 64-bit in year 2009. Maintained by kirk and jamesbond.
Simplicity Linux → A derivative of the LXPup puplet originally created by Jejy69 and carried on by peebee. Maintained by David Purse.
Puppy Studio → A commercial Puppy Linux derivative targeted at artists, mainly musicians. Maintained by l0wt3ch.