Just show that you can be thoughtful now and again I suppose lol. I mean, I'm pretty much the joke of the group - as in, I can randomly turn up and say "I'm a tree" and jump around lol - and that would be consistent behaviour, just for a laugh. But people can take me seriously too. It's on your tone of voice. Although I've never acted serious when I'm joking - I hate doing that. Like, I hate misleading people into thinking I'm serious when I'm only kidding, cus that insults the respect they're paying you. It insults their concern that they're showing. It insults their trust.
So yeh, I'd advice maybe don't act serious when you're only joking and stringing people along. I personally don't find that funny at all, only insulting. That way, when you do act serious, people wouldn't be thinking - there he goes again. But instead they'd be like - that's out of character, something's wrong? What's wrong? Then they'd listen and take you seriously.