Larry the cow is one domesticated animal you probably haven't heard of (though you may have heard of our beloved South Park cows). He is the mascot of Gentoo Linux and there's a headshot of him over at Gentoo's About page (see "Gentoo Linux... in a poster").
Now, I came across this amusing bug today, bug 27727 - bug Lary (sic) can NOT be a Cow, that insists that Larry cannot be a cow but should rather have been a bull, being male. Dictionary.com says a cow is "a domesticated bovine of either sex or any age" so that was why the bug was left as WONTFIX. Still it is weird to see Larry with udders in this thread in the Gentoo forums. Larry is probably one of the first transgender/sexually ambiguous animal mascots in Linux history.