This is a sexual term referring to a particular sex act where a man receives a blow job from a woman, cums in her mouth, and then the woman (or could be a man) pretends to swallow, then turns to embrace her partner in a passionate kiss, thereby open-mouth kissing him with his own cum in her mouth. Hence, San Francisco Switcheroo (almost gay, not quite)
Man: You gonna swallow right?
Woman: Of course
Man: You better not pull a San Francisco Switcheroo on me cause I'm not okay with swallowing my own cum.
A sex act where a woman sits on her male (or female) partner's face, and happens to be text messenging her best friend at the same time, thereby accidentally farting on his face due to not paying attention to the act.
Woman #1: So I got that message you sent me last night. You were hooking up with Pee Wee weren't you?
Woman #2: Yeah, bitch, I was so distracted by sending you a text message I ended up Nor Cal Scrumpying him!
Woman #1: Niiiiice!
Woman #2: Yeah I think he actually liked it.