In another thread I had said, "That takes the cake," which made me wonder the origin of that phrase. In looking it up, I found this site which provides origins of cliches and expressions. Here is what it says for taking the cake:
easy task/wins (the prize) - from the tradition of giving cakes as prizes in rural competitions, and probably of US origin. Brewer (1870) tells of the tradition in USA slavery states when slaves or free descendents would walk in a procession in pairs around a cake at a social gathering or party, the most graceful pair being awarded the cake as a prize. This also gave us the expression 'cake walk' and 'a piece of cake' both meaning a job or contest that's very easy to achieve or win, and probably (although some disagree) the variations 'take the biscuit' or 'take the bun', meaning to win (although nowadays in the case of 'takes the biscuit' is more just as likely to be an ironic expression of being the worst, or surpassing the lowest expectations). The variations of bun and biscuit probably reflect earlier meanings of these words when they described something closer to a cake. On which point, I am advised (ack P Nix) that the (typically) American version expression 'takes the cake' arguably precedes the (typically) British version of 'takes the biscuit'. Maybe, maybe not, since 'takes the biscuit' seems to have a British claim dating back to 1610 (see 'takes the biscuit'). This all raises further interesting questions about the different and changing meanings of words like biscuit and bun. Biscuit in America is a different thing to biscuit in Britain, the latter being equivalent to the American 'cookie'. Bun to many people in England is a simple bread roll or cob, but has many older associations to sweeter baked rolls and cakes (sticky bun, currant bun, iced bun, Chelsea bun, etc).