A twenty-first birthday is a great time to have an incredible birthday bash. This is the birthday party that everyone looks forward to and no one remembers later in life. It will of course, include alcohol, as this will be the first legal drinking party. Party invitations could include a reference to finally being an adult and partying and being "LEGAL". The party house could be festively decorated with whatever theme would fit with the birthday boy/girl. For example, if he was into "Football", that could be the theme. If a girl were into "Tennis" that could be the theme for her party and the decor would reflect that theme. Of course baby pictures of the birthday boy/girl always make an interesting feature to add to the decor of the party or the invitations. As with all parties’ food, fun, games and good company make the party. Don't forget the presents though or you will not be a popular guest. A party pinata would make a fun game for these guests who are still kids at heart.