Obvious but I'll state it: Amanda is the straight girl and Marc is the gay friend. They're a great duo and team up to insult Betty and plot together for anything. When Amanda was upset over finding her real father or was conflicted with boy problems, she would always talk to Marc and he'd be reasonable with his paternalism (85). Otherwise, they're just silly together.
In this clip, Amanda and Marc kiss in order to reenact a scene Betty describes that happened to her and a guy, but they really get into it. In the end, a few seconds later, they don't address or think anything of it because he's gay and she's into guys.
It's not actually a big deal, but to audiences it might be slightly confusing. Ultimately, I believe their relationship doesn't have the potential to reverse his homosexuality, like Shugart's article examples suggest: to be in love with someone "like you, only straight" (74). After last week's reading on Queer Theory, however, I'm starting to understand that gay and lesbian characters are not as simple to define.