During the years there were several efforts to bring Ruby to Parrot.

Pat Eyler has made the first attempt.
In 2000 he wrote a very small subset of Ruby on Parrot and called it Rabbit.
At the time, Parrot had no object support, so he was limited to string 
and numeric 'objects' and a small set of operators that posed as methods.
Sadly, there is no extant copy of the code.

Then, around 2002, Phil Tomson created the first incarnation of Cardinal. It lived
as a RubyForge project in http://rubyforge.org/projects/cardinal/.
At that time Parrot was still very much a moving target 
and it was deemed by Phil Tomson to be a waste of time to put much effort 
into Cardinal.

A couple of years ago cardindal was reborn for a time due to the 
efforts of Mark Sparshatt. But even then Parrot still proved to be too 
much of a moving target, so not much happened. The fruits of 
that effort are in http://rubyforge.org/projects/cardinal/.

More recently Kevin Tew asked whether he could use the name Cardinal and Phil Tomson
graciously accepted. The current incarnation of Cardinal lives in
https://svn.perl.org/parrot/trunk/languages/cardinal and is based on PGE and TGE.

Sources:
- http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/207872
- http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/29982