The "geep" was the first chimera made in the United States. The first of these composite animals was created in 1985 at UC Davis by fusing cells from goat and sheep embryos (goats and sheep cannot mate and reproduce naturally). Thus, a geep has physical characteristics of both species. The skeletal structure of the first geep's legs and skull were goatlike, but it had the general build of a sheep. Its coat was curly wool with scattered patches of short stiff hair.
The geeps have been very useful to researchers in providing insights into fundamental issues in developmental biology and pathology. It's also possible that the technique used to create geeps can be used to rescue some endangered species.
The geeps are not true genetic hybrids as other chimeras are; one female geep was mated with a male goat and gave birth to a genetically normal kid.
Some of the information in this writeup was gleaned from http://www.ag.fvsu.edu/html/publications/GoatCenter/goat1.htm. The rest was taken from the science dictionary at http://biotech.icmb.utexas.edu/; I oversaw the development of the dictionary (the website was mothballed in 1998) and I believe I wrote the entry this is based on.