Fun greetings can be crafted for any holiday or festival, but the message is dependent on the festival as well as the intended audience. For example, there are many websites where a person can find prewritten messages for holidays such as Christmas, Hanukkah or the New Year.
For a general and unspecified festival, a person can write a message to friends or family along the lines of "Thinking of you on this special day!" or "Wishing you lots of love." For a business colleague or more formal audience, a message along the lines of "Warm thoughts and best wishes" or a simple "Happy Holidays" would be more appropriate. If a person wants to write a funnier message to a closer audience, some messages found on Blakeflannery.hubpages.com include "This is a special message for Hanukkah. I found it on the Internet" or "I bought this envelope for you and they threw in the Christmas card for free" or "Wishing you a holiday filled with stress, cold and anger. Hey, at least this is realistic."
For Christmas in particular, a person could write a message such as "I’m not sure what you wanted for Christmas, so I just got you this card." To write a truly original message, a person would need to tie together both the theme of the holiday and a sense of humor.