Nature's full of clawed animals, but the frogs' defense mechanism is unique in the natural world because their claws literally rip through the skin when extended. They're also made of bone instead of keratin (sorry, no adamantium claws are known to exist in reality, except for this guy). Researchers aren't sure if the claws are retractable or not, and as Yong notes, they may never really want to find out:

The clawed frogs belong to a family called Arthroleptidae that were discovered in Central Africa more than a century ago. At first, people wondered if the claws just stuck through the skin as a side effect of the preservation process. Alternatively, the frogs may have used them to grip or climb. Their true function as defensive weapons only became clear when naturalists first described actually picking up and handling live animals.

Doing so is a mistake, and anyone who makes it is punished with a series of deep, bleeding wounds inflicted by the struggling animal as it kicks out violently with its claws. The ability is well known to the people of Cameroon, who only ever hunt the frogs with machetes or spears.

In the X-Men movie, Wolverine, when asked if it hurts to pops his claws, answers, "Every time." One can't help but think that the same is true for the frogs.
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However, many amphibians have extraordinary healing abilities that can even regenerate severed limbs. It may be that the clawed frogs, like their comic-book counterpart, have a 'healing factor' that closes up the wounds that open every time their claws are used.

Source: Not Exactly Rocket Science

Jackman says he's a fan of the Wolverine character, "... like everyone else. That's why I keep holding on to the character." He promises that Wolverine's arch-nemesis Sabretooth and the anti-mutant zealot William Stryker will both play a huge role in the film. The plot? A younger Wolverine "discovers the world of mutants and, ultimately, the ominous Weapon X program, which turns people into living weapons." Weapon X already played a fair part in X-Men 2 He also lets us know that there will be both familiar mutants and new faces in the film, including some big cameo roles.

The only question is, do you really want every facet of Wolverine and every dark secret exposed on film? We've already seen flashbacks of Wolvie geting injected with adamantium, we know he was part of a government project, and we know he's a rebel and a loner. Do we really need a whole film to tell us why? We'd prefer a film that follows the storyline from the comics where Magneto pulls all the metal out of his body, and it nearly kills Logan. Later, during a Danger Room training sequence, he discovers he has bone underneath those claws. First Look: Gavin Hood's X-Men Origins: Wolverine [First Showing]

While Brian Cox was firmly tied to Wolverine's background as William Stryker in X-Men 2, the studio has been talking to Liev Schreiber about taking the role over, since this film is set seventeen years before the first X-Men film. Cox was willing to take the role back, and was hoping they could make him look younger via CGI, like they did with Professor Xavier and Magneto in X-Men 3. Although, that scene made them look like smooth-skinned mannequins that were shot on a lens coated in vaseline. Yuck.

The film aims to answer questions about his background, which was also the theme that ran through the first two films. However, that's about the only thing it has going for it right now. Fox announced that the title has been officially changed from Wolverine to X-Men Origins: Wolverine for reasons we can't understand. Maybe Fox equates movie success with the amount of space the title takes up on a marquee.

How in the world will this film be ready when they turn the cameras on in just a few weeks? Thanks to the writer's strike, there won't be any "day of" rewrites going on. If they encounter any messy problems, they're just going to have to try and do what Hollywood does best: fix it in post. We say, stick this back on the shelves and wait out the strike.