Happy Loman is the overshadowed son of Willy Loman. He has lived his entire life under the shadow of his brother Biff who is older, who was successful as a high school football player, and whom Willy vicariously sees as a reflection of his own ego.
Yet, Happy has not been able to make a mark in Willy's life. For this reason, he resorts to making up stories that would please Willy to hear. Happy also likes to ease his mother's afflictions and downplays the tensions of the family. That is his basic role. As a result, it is also Happy who comes up with the idea of inviting Willy to celebrate the so-called business meeting between Biff and Bill Oliver in Act II, Scene 7. In this scene, Happy displays all the evidence the audience needs to conclude that it is Happy, and not Biff, who is the most like Willy Loman.
The first thing that we see is Happy's haughty and semi narcissistic behavior. He sits at the bar charming his way around the room and telling fake stories of his successful career, his many travels, and of his talent to attract women. As he does this, he charms Letta, a woman whom he does not know, with champagne and flirts with her tremendously. He then calls Biff over and lies even more about Biff's own talents and successes.
This indicates that, like Willy, Happy gives value to superficial things, such as job success, as if they were the most important things in life. Happy's insistence in making himself appear someone that he is not is another deceitful tendency that he inherited form Willy Loman; it is as if, both, Willy and Happy simply cannot go through life being true to themselves and proud of who they really are.
Another demonstration of Willy and Happy's shared system of values, is that none of the men feel any shame in lying to a person's face, per se. Lying is a natural habit to Willy and Happy, and a demonstration of their lack of morals.
Their shallowness extends to their treatment of women, whom they see as objects made to feed their ego, only to deject the later with no remorse. Willy Loman, throughout his lifetime, was particularly needy of the approval of women, even though he was already a married man.
Hence, Miller adds the characters of Letta and Miss Forsythe to prove that very point. The moment Letta enters the play, Happy completely changes his game plan, from caring brother and son, to selfish womanizer. He completely forgets the original purpose of the meeting and, instead, drags Biff out to go out with the girls, leaving Will behind. Like his father, Happy could care less about family time if there is a chance to do something that would make him feel better about himself.
Conclusively, shallowness, selfishness, lies, and lust are the main values that Happy and Willy share in just about every single aspect of their lives.