well in this case it's an animated sheep with the exact same name (granted it's quite an obvious name to give a sheep) - but it looks virtually identical in every respect... except that he's standing on 2 legs
And minus the woolly jumper gag (although that helps very little... releasing somebody else's IP-but-without-a-certain-feature hardly provides protection). Sheep are kinda famous for looking and acting the same but, all messing about (see previous smiley) aside, I have to admit that I personally wouldn't risk trying to publish that character as-is. Even if skn3[ac] is correct in his assertion that his character predates Aardman's, he has still failed to protect his copyright via a legal challenge and may have lost it by now. Perhaps someone more familiar with the legal system could clarify where skn3[ac] is likely to stand.
Luckily, the character is different enough for it to not matter. Notice the color in fur, and the fact he stands on two legs, and will be wielding an uzi or rocket launcher XD
This just makes things worse. Using a recognisable characters out of context, say Mickey Mouse pimping Minnie and Pluto to Goofy (don't dwell on it), is arguably an even greater transgression of IP than just copying them outright. Aardman wont want (its) Shaun T. Sheep associating with the gratuitous violence that (skn3[ac]'s) Shaun T. Sheep will be tooled up for. I would get a legal opinion on whether there is enough difference between the two Shauns before putting any more time and effort into the character and CERTAINLY approach the intended publisher to find out if they view such content as contentious. If nobody will touch your game due to IP issues then, at the end of the day, all else is moot.