Walter Carol "Walt" Miller (born April 3, 2971) is one of the recurring antagonists in Futurama. He is the oldest and most intelligent of Mom's three sons. He owns 0.1% of MomCorp, while his brothers Larry and Igner own the remaining 0.2%. He is the most like his mother in personality, with deeply devious and malicious tendencies. He has on multiple occasions abused his younger brothers. In his mother's absence, he takes charge of the situation. What keeps him in line is his apparent Oedipus Complex - he has an unhealthy admiration for his psychotic mother, despite her regular abuse of him, and has even admitted that some day, he wishes to marry a woman like her.
Despite Walt's supposed intelligence, the plans he concocts are markedly ridiculous, such as impersonating Mr. Panucci to elicit information from Fry and having the trio pose as owl exterminators to get the anti-backwards crystal when he knows absolutely nothing about owls or their extermination. They only work because it's Fry the plans are mostly directed at.
Another example of Walt's childishness is shown in the episode "Mother's Day". When he learns that Professor Farnsworth is the man who broke Mom's heart, like a child whose parents have separated, he assumes that bringing Farnsworth and Mom back together should be a simple task that will make her happy and thus everything will be alright again.