Short List of How to Ask for "Extras"
1) When excited, my privates excrete gold bullion worth approximately $400/ounce, but it only becomes chemically stable when immediately mixed with saliva. Want some?
2) For medical reasons, I'll need to apply a salve to your privates before we can continue. Due to the nature of the salve, it needs to be applied via my tongue. Please lie back.
3) I'm doing a research project on the relationship between tonsellectomies and halitosis among women in the age range of 18-29. For this project I will need you to open up and say "ah" for a duration of approximately 20 seconds. As I will also need to observe pupil dilation during the process, I will be performing the procedure at close range using my tongue as the instrument of measurement. Please stand directly in front of me and open your mouth.
4) I'm really fucking horny, you're so smokin' hot, and as it's the fourth time I've seen you and I've been over-tipping all along, how's about taking this to the next level?
Take your pick.