20 years at a job is reason enough for a celebration, party or festive gathering. Decide whether this will be a casual event with munchies and snacks, a cocktail hour or formal dinner. Match the event with the tone and taste of the person celebrating the anniversary as well as the office or company as a whole. Gifts are not required, however a group gift from the office would likely be appropriate and appreciated.
The event could be a surprise for the worker or could be a planned event. The party could be held at the office, if space allows, a lounge or restaurant, or if the office is close-knit, at an employee's home. Choose a theme to decorate the party. Consider using the year they were hired for inspiration. If they began working in the 1970s, for example, choose '70s-themed decorations. Hang a disco ball and play '70s disco music. Invite guests to come dressed in 1970s attire. Hang a photo montage on the wall profiling the celebrated worker's journey over the past 20 years. Include photos of him at company picnics, Christmas parties and giving presentations.
If the office would like to give the worker a gift, consider choosing something keepsake-orientated. Research the actual first day of the employee and find this date in the local library's newspaper archive. Choose a page of the paper with an exciting or interesting event and make a copy and have it framed. Another option would be to give this person who has worked so long for two decades a day of relaxation and pampering. Present them with a gift token for a day at a spa, complete with a massage and facial. For an avid golfer, give them a gift token for a round at a local course.
To thank this worker for all that he has done and contributed to the company, take a moment to raise a glass and offer him a toast. This should be prepared by a co-worker that knows him well, or a supervisor that knows his work ethic. Keep the toast appropriate to a professional environment and don't drag it out by listing every accomplishment and contribution he has made over 20 years. Highlight the best points and offer a heartfelt thanks for his efforts and commitment.