This week brought news that Twitter’s latest celebrity recruit is Pope Benedict XVI. His first Tweet, launching the Vatican’s news service and praising Jesus, was a cut above the standard debut Tweet, which tends to be a variation on “Hello,” “So how does this thing work?” or the self-evident “I’m on Twitter!”

It was delivered via the Vatican’s official Twitter account - no doubt the only option left, since the Twitter handles @popebenedict, @popebenedictxvi, @pope, @thepope, and even @ratzinger and @josephratzinger were already taken, mostly by people pretending to be him. The Holy Father just learned a valuable lesson in coming late to the party.

The Pope will now begin to explore the world of Twitter, and cycle through all the usual newbie reactions: I don’t get it; why isn’t anyone answering me; this is boring; these people are idiots; stuff this; hang on, this is the most awesome thing ever; people need to know what I think about Justin Bieber; what’s with the “#”? Historically, this will be the first time these reactions are uttered in Latin.

The final question – what’s with the “#”? – is common to all newcomers to Twitter. The hash precedes a word or phrase, forming a hashtag. It’s flummoxing at first, but once you get used to it, you realise it’s possibly the greatest invention since the abacus.

The hashtag is a searchable term, helping you follow what anyone, anywhere, is saying about a given subject. Whether it’s a breaking news story (#nzearthquake) or your favourite pop star (#rebeccablack), the Twitter user has immediate access to the reactions of complete strangers, negating any need for expert opinion or competent analysis.

Tweeters (sorry, but I just can’t come at ‘Tweeps’) also use the hashtag ironically. It looks like they’re using a searchable term. But they’re not, really. They’re just saying something extra about themselves, often self-deprecatory. Like this:

This Tweeter is not really taking part in an ongoing discussion about their intelligence. They’re just admitting to their followers that they are an idiot. You’re not really meant to click the hashtag.

(Clicking the #iamanidiot hashtag still works; you will see thousands of users publicly admitting to being idiots without expecting that you would actually click that hashtag. Proving their point.)

For my money, the most joyful application of hashtag technology is the communal joke. Someone declares a theme; everyone else joins in, trying to top each other for wit. The unspoken aim is that your tweet is so funny, your followers will re-tweet it to their followers, and so on. Write enough re-tweetable tweets, and you’ll collect more followers. On Twitter, followers are gold.

My favourite type of joke hashtag is the Random Compound Hashtag, or ‘RC#.’* It works like this: two unrelated things are combined.

That’s pretty much it.

I might need to explain.

Recently I enjoyed the short-lived home-grown hashtag #trammovies. The aim: tweak a movie title so that it refers to trams. Coined by user @miranda18may, a bored Melburnian on her way home from work (guess how), it was embraced by locals before finding an international audience. Many of them had little idea what the hashtag was about, but tried to join in anyway. Good on them.

“Why ‘#trammovies’?”, you may ask, in a dizzying blur of punctuation marks. This is the fun of Random Compound Hashtags. There is absolutely no reason for #trammovies. The pursuit is completely pointless. That’s why it’s fun. The answer to "Why '#trammovies'?" is: "Why not '#trammovies'?"

Thus we end up with hashtaggy delights like #fishbands - band names with fish references (“Public Anenome”) - and #cannibalsongs – songs referring to cannibalism (“I Should Be Souvlaki”). You’re probably catching on. A good RC# is infectious, hilarious, and just about the last place in the civilized world where you’re still allowed to reach for the occasional mild racial stereotype.

(#cannibalsongs was another Aussie invention by user @kynanb. #fishbands’ origin seems lost to the mists of time, unless someone can enlighten me.)

What many users fail to grasp about RC#s is that it’s not an ‘I-Spy’ competition where you have to find real-life things fitting the description. You invent them.

The 1980s Aussie classic Malcolm is in fact an actual, real-life #trammovie, but try that on Twitter and no one is impressed. Hit them with Bogie Nights, however, and you score the jackpot. Bogie Nights (a) is made-up; (b) is funny, if you get it; (c) meets the ‘movie’ criteria, being based on Boogie Nights; and (d) contains a tram reference: ‘bogie.’

Scratching your head? As my dad would tell you in far too much detail, the ‘bogie’ is the part of a tram that the wheels are attached to. Our Bogie Nights contributor scores massive bonus points for obscure knowledge of subject matter. Pity my Dad isn’t on Twitter to appreciate it.

(A search suggests Bogie Nights was coined by user @19tram. Many of Melbourne’s trams have their own Twitter accounts. Being an inanimate object is no hindrance to using Twitter.)

Alas, cleverness on this scale often leads to a collective shrug from people who don’t get it. One can effectively ‘clever’ oneself out of the retweet market. The ignorant masses could figure it out, but they’re too busy racking their brains to come up with Tramspotting even though that’s been done by ten thousand people already. (@hollyjasminetil beat them all.)

That’s the trouble with these RC#-fests. Users are so keen to join in, they fail to consider the possibility that their masterpiece has already been submitted. Tweeting your contribution without first using the search function to check if you’ve been beaten to the punchline is an insult to the hashtag creator, disrespectful to any Tweeter who beat you to it, and can actually destroy the internet. You are trying to claim gold for coming second. You are the Jordan Paris of Twitter.

Here’s a quick rule of thumb: if it took you less than a minute to think up, it’s been done.

And so I commend both Twitter and the Random Compound Hashtag to Pope Benedict, and everyone else. You can join in next time you're waiting for a tram, or waving at pilgrims from your balcony.

Just be sure to obey the Seven Commandments of RC#ing:

I. Thou shalt meet all aspects of the random compound hashtag criteria.

II. Thou shalt amuse.

III. Thy contribution shalt be thine original work.

IV. Thou shalt endeavour to determine that thine idea hast not been previously submitted.

V. If thy neighbor hast contributed something similar, but not the same, thou shalt ask thyself what the funny bit is. If it be basically the same joke, thou shalt not steal. If it be similar in theme but thine is a definite improvement, then, OK, go ahead, but don’t come crying to me if thou getst flamed.

VI. Thou shalt spell the hashtag correctly, lest thine efforts go unseen by they whom thou art trying to impress. In which case, #thouartanidiot.

VII. Thou shalt retweet thy neighbor as thou wouldst have thy neighbor retweet thee. Twitter karma, or ‘Twarma’, be thine friend.

Now go forth and #twultiply.

* I completely made up the term "Random Compound Hashtag."

Follow Gerard's hilarious RC#s at @drjavabeans