Danny, the informal name for Danny Wallace. The Leader is almost exclusively referred to as ' Danny', rather than Danny Wallace, or Mr Wallace, as we see this as more a friendly acquaintance than a business one. Even though he is our Leader, and we are supposed to do his bidding. Once you get to know him well, you too can call him Danny. Most of us do.
For most purposes, it is Danny, the friendly chap who goes out for drinks with friends and strangers, makes important phone-calls whilst still in his underwear, and pursues silly boy projects that we have joined, rather than the professional entity Danny Wallace, a renowned journalist who used to work for the BBC, and who writes good books. Of course, it is the same person, but it's important to distinguish the cheery version we follow from the name and professional set up under the page dedicated to his full name.
The Join Me anthem implores you to join Danny, rather than Danny Wallace or 'The Leader'. That's how informal it is, even the anthem refers to him simply by his forename. Sure, you might get him confused with another Danny, but if you're that careless you probably haven't been paying much attention this far, have you?