A sexualized version of "in for a penny, in for a pound." Means almost the same thing as the original saying but in a sexual context as aforementioned. In context, it references sex with or without protection (in this case, without), and since it was done before might as well double down and do it again regardless of the consequences.
This was used in Team Four Star's, Dragon Ball Z Abridged: Episode 60 Epilogue.
Bulma: "But after the first time, I just thought; well, in for a penny, in for a pounding."
Trunks: "Ahhh!"
Bulma: "And I really was."
Trunks: "AHHHHHHHHHHHHHH!"
Calling someone a penny is an insult. First you say, "you're like a penny", the person will then ask why. You then proceed to say that they are invaluable, flat, two-faced and is always in someone's pants. This insult is normally done to one of a female gender.
This is a script of a random dude calling someone a penny
Bitch: You don't know me! You cant even describe me in one word.
Random dude: Your like a penny.
Bitch: WTF????
Random dude: Invaluable, flat, two-faced and always in someone's pants.
Term used to describe how quick one is on something. Much like the term stink on shit or white on rice. Whalen on a penny refers to the cheapness of a Dick Smith named Jeff. If one were to let a penny fall from their hands it would never hit the ground in the presence of Jeff.
Boss: Hey Peter are you going to have those TPS reports for me by lunch?
Peter: Chill out Lumberg! I am on it like Whalen on a penny.