Especially for a LRP. I mean, yes, he's a white mouse, and yes, mice are freaking cute... but it's hard to take a giant adorable white mouse seriously.
Unless he's wielding a really big axe.
My apologies that the main photo isn't so great, but at least we've now been able to take a few better pictures.
Charlie Mouse has been my husband's RP character in the Lorien Trust LRP games over there for quite a while now, usually played with a skaven (rat-man) mask (far less freaking cute, though). I attempted with rather limited time to make him a genuine white mouse mask for the Heartland Games in 2005, which I was lucky enough to attend (if you can stand mind numbingly cold temperatures...)
The mask is unfinished, mostly just lacking neck-fur, but is pretty typical of my masks. It is made of plastic mesh, and the jaw moves (quite nicely on this one, in fact!).
The eyes are made from the lenses of sunglasses, the theory being they would be easier to see out of than plastic mesh. I don't recommend this idea in practice though, as poor Robbie fogged them up just breathing normally inside of the mask.
Not a lot else to say on this one... possibly with a little airbrush work he can look just a tad fiercer... but I don't think it's possible to make a big white mouse look... uncute...
A couple of side-notes, though... the LRP weapons they use are incredibly cool! The axe you see him holding is made mostly of foam and latex, with a carbon-fiber rod inside for structure. You could smack people all day with those weapons (and indeed, we did), and never hurt anyone — yet they look incredibly realistic.
Also, that is real chain mail he's wearing. I tried it on, and it is HEAVY. He made it himself. And yet he still insists he has no talent. BAH!