Mark gave his girlfriend Michelle his gag gift for their anniversary before going on a date. Michelle opened it up and saw some inflatable boob pads. They were cheap, looked nothing like boobs, and would merely have a somewhat boob shape when inflated. It also had a band so you wouldn't need a bra to keep it on your chest.
Michelle chuckled so Mark said "Hey, you gave me that weird dildo thing. I thought this would be kind of fun." Michelle looked in the box and saw a small ball that was supposed to be a pump, but was missing a tube.
Michelle said "Well you got a defective product. Unless you wanna blow up my boobs with your lips?"
Mark thought for a second and then said "As romantic as that sounds, I remember blowing up beach balls and that'd get awkward fast." Michelle with the inflation ball in hand looked at her new fake boobs and squeezed the ball, and then noticed the fake boobs seem to inflate a little.
"Hey, I think it remotely inflates." Mark looked confused since it wasn't like there were batteries or whatever but as she squeezed the ball the thing did in fact inflate a little. Michelle then unplugged the plastic stopper and deflated the boobs and then tossed the inflation ball to Mark. Michelle strapped the inflatable boobs under her shirt and then said "Why don't you pump up my boobs and then we can go on our date?" fully intending on just ditching the fake boobs.
Mark looking at Michelle's boobs pressed in the inflation ball and saw that her chest pushed out her shirt a little further. Michelle felt the tightness around her chest, but it took a few presses before she really began to understand that something weird was going on. It felt like there were two pressures instead of one. She had merely expected the feeling of the plastic pushing against her real boobs, but it was more like her boobs were pressing out against her clothes as the straps of her bra were digging into her back a little. There was also a pressure from within her boobs. Mark was absorbed in seeing how big those fake boobs got, how high her shirt lifted, an- "Stop! I think something snapped or popped." Mark stopped pumping then looked at Michelle and noticed that her neckline was showing a decent amount of cleavage, and Mark remembered that Michelle's boobs weren't that big.
"Um... I'm not sure I was inflating the fake boobs." Mark said as the two of them realized what was going on and started thinking about what they were going to do about them.