(what a silly question!)

"The Wombat is a Joy, a Triumph, a Delight, a Madness!"  ~ Dante Gabriel Rossetti (in an 1869 letter to his brother)


From William Michael Rossetti's Family Letters, with a Memoir:

IT has often been stated that my brother, at Cheyne Walk, kept from time to time a large number of animals.  This is entirely true.  Being fond of "beasts," and having a large garden, with plenty of space for accommodating them either in the open or in corners partitioned off, he freely indulged his taste.  He had no particular liking for an animal on the mere ground of its being "pretty" -- his taste being far more for what is quaint, odd, or semi-grotesque.  Dante's specimens of fauna however were often very sightly, as also often funny and out-of-the-way.  I will name some, as they happen to come; others have passed from memory into the limbo of oblivion.

There were a Pomeranian puppy named Punch, a grand Irish deerhound named Wolf, a barn-owl named Jessie, another owl named Bobby (described by Christina as "a little owl with a very large face and a beak of a sort of egg-shell green"), rabbits, dormice, hedgehogs, two successive wombats, a Canadian marmot or woodchuck, an ordinary marmot, armadilloes, kangaroos, wallabies, a deer, a white mouse with her brood, a racoon, squirrels, a mole, peacocks, wood-owls, Virginian owls, Chinese horned owls, a jackdaw, laughing jackasses (Australian kingfishers), undulated grass-parrakeets, a talking grey parrot, a raven, chameleons, green lizards, and Japanese salamanders.

Persons who are familiar with the management of pets will easily believe that several of these animals came to a bad end.  Punch the puppy would get lost; one or other bird would get drowned; the dormice would fight and kill one another, or would eat up their own tails, and gradually perish; Wolf the deerhound could get no adequate exercise, and was given away; the parrakeets were neglected at some time that
Rossetti was absent from home, and on his return they were found dead.  Other animals, owing to their burrowing or reclusive habits, disappeared.  An armadillo was not to be found; and the tale went -- I believe it to be not far from true -- that, having followed his ordinary practice of burrowing, he turned up from under the hearthstone of a neighbour's kitchen, to the serious dismay of the cook, who opined that, if he was not the devil, there was no accounting for what he could possibly be.  The racoon, as winter set in, made up his mind to hibernate.  He ensconced himself in a drawer of a large heavy cabinet which stood in the passage outside the studio-door.  The drawer was shut upon him, without his presence in it transpiring, and after a while he was supposed to be finally lost to the house.  When spring ensued, many
mysterious rumbling or tramping or whimpering noises were heard in the passage, or in the studio as coming from the passage. My brother mentioned them to me more than once, and was ready to regard them as one more symptom, by no means the first or only one, that the house was haunted.  At last, and I think by mere casualty, the drawer was opened, and the racoon emerged, rather thinner than at his entry.

*            *            *

The beasts upon which Dante's affections were prodigalized were the first wombat and his successor the woodchuck. The second wombat, having died immediately, counts for little.  No more engagingly lumpish quadruped than the first wombat could be found, and none more obese and comfortable than the woodchuck.  They were both tame, especially the woodchuck; and Dante would sit with either in his arms by the half-hour together, dandling them paunch upward, scratching gently at their cheeks or noses, or making the woodchuck's head and hind-paws meet.  With the wombat no such operation was possible.  Each of them was his housemate for some time, and each expired without premonition.  I do not assume that my brother wept over them, but certainly "his heart was sair."  For the wombat (not having yet seen it) he wrote from Penkill Castle the following quatrain: --

"Oh how the family affections combat
Within this heart, and each hour flings a bomb at
My burning soul!  Neither from owl nor from bat
Can peace be gained until I clasp my wombat."

Of course, a more cynical and less historical explanation for the Rossetti Archive's love of wombats exists, embodied here in this entry from the New Hacker's Dictionary:
WOMBAT /wom'bat/ /adj./

[acronym: Waste Of Money, Brains, And Time] Applied to problems which are both profoundly uninteresting in themselves and unlikely to
benefit anyone interesting even if solved. Often used in fanciful constructions such as `wrestling with a wombat'. See also crawling horror.