Robin: Look, guys, we've got this covered, okay? No one's gonna get hurt. We set up ground rules.
[flashback to Ted and Robin in the apartment:]
Ted: Rule number one, this is strictly a physical relationship. There are no feelings involved, okay?
Robin: Oh, please, that's like telling the Fonz to be cool.
Ted: And since it's just physical, we don't have to worry about romance, right?
Robin: Hell, no. Ooh, we can do it while we watch TV!
Ted: Totally! And we can multi-task. You know, use the sex to spice up otherwise dull activities.
Robin: Like folding laundry.
Ted: Paying bills.
Robin: Cooking dinner.
Ted: That doesn't seem hygienic.
Robin: Yeah, not that one.