The COW programming language is an esoteric programming language created by Sean Heber in 2003. It is a Brainfuck variant designed humorously with Bovinae in mind. COW has twelve instructions (four more than Brainfuck) and is Turing-complete. Most instructions are moos, only the capitalization varies: mOo, moO, mOO, Moo, and so on. MMM, OOO, oom and OOM are the exceptions. All other character combinations are ignored and treated as comments.
Here is the code required to generate the Fibonacci sequence:
MoO moO MoO mOo MOO OOM MMM moO moO MMM mOo mOo moO MMM mOo MMM moO moO MOO MOo mOo MoO moO moo mOo mOo moo