As for 'large', there can be only one candidate. What will surely be UK mammal of the year - the long-staying Walrus in Pembrokeshire. I wonder whether any mammal has ever been more widely twitched in the UK. What a beast.
The UK has been graced by several wintering Little Buntings, and I enjoyed the brace on a Surrey heathland.
For those whose childhood encompassed the 1980s, Eddie Little and Eddie Large were a not particularly stellar comedy duo with contrasting statures. This blog features creatures of analogous size disparity. Last weekend, I caught up with two long-staying local gulls on the same Norwich broad: Kittiwake and an adult Little Gull, the latter moulting into summer plumage.