The Lion and the Unicorn are symbols of the United Kingdom. They are, properly speaking, heraldic supporters appearing in the full royal coat of arms of the United Kingdom. The lion stands for England and the unicorn for Scotland. The combination therefore dates back to the 1603 accession of James I of England who was already James VI of Scotland. By extension, they have also been used in the arms of Canada since 1921. In the Middle Ages and Renaissance, it was commonly described as an extremely wild woodland creature, a symbol of purity and grace, which could only be captured by a virgin lady.
The Lion and the Unicorn Wikipedia
The traditional legend of enmity between the two heraldic animals is recorded in a nursery rhyme which has a Roud Folk Song Index number of 20170. It is usually given with the lyrics:
The lion and the unicorn
Were fighting for the crown
The lion beat the unicorn
All around the town.
Some gave them white bread,
And some gave them brown;
Some gave them plum cake
and drummed them out of town.
The legend of the two animals may have been intensified by the Acts of Union 1707 and it was one year later that William King (1663–1712) recorded a verse very similar to the first stanza of the modern rhyme. This seems to have grown to include several other verses. Apart from those above only one survives:
And when he had beat him out,
He beat him in again;
He beat him three times over,
His power to maintain.
This rhyme was played upon by Lewis Carroll, who incorporated the lion and the unicorn as characters in Through the Looking-Glass. Here, the crown they are fighting for belongs to the White King, which, given that they are on the White side as well, makes their rivalry all the more absurd. Carroll subverts the traditional view of a lion being alert and calculating by making this particular one slow and rather stupid, although clearly the better fighter. The role of the Unicorn is likewise reversed by the fact that he sees Alice as a "monster", though he promises to start believing in her if she will believe in him. Sir John Tenniel's illustrations for the section caricature Benjamin Disraeli as the Unicorn, and William Ewart Gladstone as the Lion, alluding to the pair's frequent parliamentary battles, although there is no evidence that this was Carroll's intention.
The rhyme is also the basis of an episode in the novel Stardust by Neil Gaiman, in which the protagonists of the novel, Tristran Thorn and Yvaine, witness a lion and a unicorn fight over a crown during their travels through an enchanted forest. The accompanying illustration by Charles Vess applies an Art Nouveau style to a realistic depiction of a lion attacking its prey.
In the Batman: The Animated Series episode "The Lion and the Unicorn", a terrorist kidnaps Alfred Pennyworth and drugs him, attempting to get a secret code he learned during his time in the British Secret Service. Pennyworth begins reciting the verse among others- both to resist the drug and to cover the fact that the code itself is part of the verse, thus when his resistance breaks down it is not immediately clear.
In the anime and manga series Pandora Hearts, the Lion and the Unicorn are named Leon and Equss, the chains of Lottie and Sharon Rainsworth.