Starting with a banana, finishing with a cock

Mary Rock is active all the time. When she's not busy, you'll find her out for a run, riding a bike, or taking a walk in the park. She decided to go on an adventure today wherever the road takes her and wouldn't you know it? She got a flat tire! She's has a bike pump with her, but it doesn't seem to work. What a mess! Luckily for Mary, a guy comes along and gives a helping hand. He offers her a banana, seeing as she's been on the run all day. Mary wants to pay him back so as soon as she eats the banana, there's another one coming her way, better, harder, and way more delicious. I guess she found a way of maintaining her daily exercise schedule.