Whether you're getting back at a friend for the pranks he pulled on your birthday or just in for some good-natured ribbing, a 40th birthday offers an ideal opportunity. With this birthday, many people realise that they are entering their middle-aged years and take a look back to evaluate their accomplishments. This leaves the door open for many over-the-hill jokes, pranks and just plain good fun. The best way to ensure you embarrass a 40-year-old is to take charge of the birthday party plans.
Plan a surprise party. The easiest way to ensure your friend will be thoroughly embarrassed on their 40th birthday is to surprise them. If they don't know what is coming, they can't prepare for the embarrassment. After you have your guest list assembled, head to the party store and find the most appropriate over-the-hill party invitations. This will let guests know what type of party they're in for.
Decorate in an over-the-hill theme. The room should be filled with decorations that remind the birthday girl that she is officially middle-aged. Black is an appropriate colour to decorate with, as this theme usually, and humorously, symbolises mourning. Decorate with black balloons and encourage guests to wear black hats that say "over the hill." Cover any tables with black tablecloths and hang at least on banner that says "over the hill." Arrange the chairs around the guest of honor's table, as if guests were attending his funeral.
Prepare a slideshow of the person's life. For the main event, you may need to enlist help from his siblings or parents. Find the most embarrassing pictures from his life, including those bath-time baby pictures and awkward prom snapshots. Use a computer program that allows you to create slideshows, such as Microsoft PowerPoint, and burn the completed slideshow to a disc to be played at the party. If you don't have this type of program, you can create a slideshow on a website like Slide or Slideroll, then use an HDMI cable to connect your computer to the television and share the images with everyone.
Encourage guest participation. To thoroughly embarrass your 40-year-old friend, you'll need to enlist the help of all her friends and family. Ask all guests to come prepared with a story to tell about the birthday girl, and make sure they know there will be prizes given for the most embarrassing story.