Moe Blum was known to be an enforcer for the Black Mask, but presumably was forced to find other avenues of work after the crime lord's untimely demise. He was enlisted by Tweedledum and Tweedledee to join their Wonderland Gang, functioning as "The Walrus" alongside of a costumed woman known as The Carpenter. He debuted in April 2008.
His first appearance is in Detective Comics #841, where Batman investigates a growing new team of costumed crooks, "The Wonderland Gang". Led by the Mad Hatter and featuring Tweedledum and Tweedledee, they quickly amass high-class muscle from all over Gotham dressed as different Lewis Carroll characters, such as the Carpenter, the Walrus, the Lion, the Unicorn, and the March Hare. Finding the crimes somewhat amiss, Batman eventually tracks the gang down to the House of Mirrors at the Gotham Amusement Park. He then goes in and confronts the gangs real leaders, Tweedledum and Tweedledee. While Batman is battling the rest of the Wonderland gang, Tweedledum and Tweedledee both escape outside only to be subdued by the Mad Hatter, and all of the gang was brought to justice by Batman and the GCPD.
He makes an appearance with few of his new friends, the Carpenter and the Tweeds, in Detective Comics #847, where they made another attempt to commit their crimes, but while Batman was busy going against Hush, Nightwing, Robin, Catwoman, and Zatanna apprehended the Wonderland Gang once again.
When the Carpenter was asked to be part of the Director's group, she remembers the times of her 'Wonderland Gang', and in that flaskback, she remembers her great co-worker, the Walrus.
In Other Media
Although he isn't in the game, he appears with the Tweeds, the Mad Hatter, and the Carpenter, in the 2nd digital issue of the Arkham City comics. They tried to escape by themselves out of Hugo Strange's new prison, consisting of both Arkham patients and Blackgate prisoners, Arkham City.
He briefly appears in the Arkham Unhinged comic "Vicki in Wonderland". He tries to attack Batman but Batman defeats him.