3rd Rock from the Sun - Season 5 Episode 7

Mary is horrified when she learns that Dick has been pocketing all the tip money she has left at restaurants, but Dick is baffled by the concept of tipping, and attempts to re-invent it by placing a stack of one dollar bills on the table and informing the waitress that when she pleases him, the pile will grow, and when not, it will shrink. Mary, however, informs him that this idea is demeaning. Meanwhile, Sally goes on the pill after Tommy informs her that she could become pregnant by having sex with Don, but begins to experience erratic mood swings and food cravings.