It can be hard for Mac trying to guess safe ways to surprise Fluttershy, but when she leaves a pair of lifeguard swim trunks, a whistle necklace, and a lifeguard's floatie thing on his side of the bed then loudy anounces that she's going to take a long bubble bath and doesn't think she'll lock the door, he feels pretty safe guessing what she wants.
Fluttershy: "This isn't a beach, it's a bathtub."
Big Mac: "Ah'm sorry, wut was that?"
Fluttershy: "This isn't a beach, it's a bathtub."
Big Mac: "Didn't quite catch that."
Fluttershy: "………………… TAKE ME NOW, YOU GORGEOUS STALLION!!!"