Place it as the second beat in a reaction edit, after Oh My God Wow sets up the surprise and before Nelson's Ha-Ha! closes the joke. It also works after Eww Brother Eww when the reveal needs a second reaction, keeping the sequence short and focused on one person's response.
About this sound
This is a short spoken reaction clip, lasting about two and a half seconds, in which a voice delivers the line 'Oh, that's gay' in a flat, knowing tone. It lands as a playful, teasing callout, the kind of quick aside that makes a joke feel sharper without turning mean. It works best as a light, amused reaction rather than a serious comment.