Humorous things to write in an invitation include "Nothing makes you more tolerant of a neighbor's noisy party than being there" and "Live for today, plan for tomorrow, party tonight." These are suggestions from SearchQuotes.com.
Other ideas include "When you invite the whole world to your party, inevitably someone pees in the beer" and "A holiday cocktail party is where some stranger will learn more about you in an hour than your spouse has learned in a lifetime."
Humorous quotes from famous people suitable for including in a party invite include "A gathering held to enable forty people to talk about themselves at the same time. The man who remains after the liquor is gone is the host," said by Fred Allen, and "At every party there are two kinds of people - those who want to go home and those who don't. The trouble is, they are usually married to each other," said by Ann Landers. There are also humorous proverbs such as "Where the hostess is handsome the wine is good," which is a French proverb according to QuoteGarden.com. Other proverbs include "Many seek good nights and lose good days" and "We're fools whether we dance or not, so we might as well dance."