Sit-coms can challenge gender roles in a few different ways. They can feature characters that challenge traditional gender stereotypes, such as a stay-at-home dad, a female breadwinner, or a gender-nonconforming character. They can also feature storylines in which characters confront traditional gender expectations, challenge societal norms, and find ways to create more equitable relationships.
Today's sit-coms often challenge traditional gender roles while still accepting them. For example, the hit show The Big Bang Theory features a female lead, Amy, who is a successful scientist and highly educated. Her male counterpart, Sheldon, is more socially awkward, leading to a dynamic where the roles of traditional gender stereotypes are reversed. Another example is Modern Family which features a gay couple raising a child and challenging traditional gender roles in the process.