Mondo Zappa enjoys the occasional drink with a lady between missions. Apparently the reason he does is that as he stares at their breasts and legs, he works up the courage to give them a gift. In return, he can get a new gun arm!
Here's a look at the mechanics of the first gigolo mission, including a look at what happens when you stare too long:
There are several of these "gigolo" missions, including one with a vampire, for some reason. You can go back and re-do these missions as many times as you want, but the price for the gifts goes up every time you buy one. Oh, did I mention there are also X-ray glasses? Because there are. Take a look: