You get a mischievous feeling, and without warning, you coat your girlfriend in the spray. Instantly, you feel your entire body change. First, you feel the bones changing in your hips, and gradually, they get wider. Next your chest gets heavier, and two breasts fill your shirt, stretching it a little. You felt arms and legs grow a little thinner, and lose all their hair. Your hands and feet shrink next, and your fingernails and toenails are suddenly coated in pink nail polish. Your faces shifts a little, becoming more feminine, and your hair grows out. Your ass becomes a little more padded, and your waist narrows a little. Finally, you peer down to see your penis and testis contract into your pants, and you feel them inside of you, obviously turning into girl organs. Once your body is completely swapped, your clothes seem to disappear, and are instantly replaced by Denise's.
You look across at your girlfriend to see her in your body.
"Well, wasn't that fun!" You yell in your new, girly voice
Denise coughed a little, then said "What are you talking about? What'd you spray me for?"
"Obviously, to swap bodies!" You yell again, barely able to contain your excitement.
"What are you on about? You want to swap bodies with me?"
"Umm, I kinda just did." You said, a little confused now.
"When? I don't see you having my penis, and I certainly don't have your boobs!"