a cracker (n): a small paper tube which is pulled from each end by two people at Christmas time. It makes a sharp bang when it is pulled and inside there is a small prize and usually a paper hat and a joke written on a small piece of paper
to cross (v): to mix or blend something together
to crack someone up (v, informal): to make someone laugh
to look sharp (v, informal, to talk about someone's clothes): to look good, stylish or fashionable
frostbite (n): injury to skin and tissue from being in freezing temperatures