• An Elon Musk tweet about cocaine and Coca-Cola is said to have been framed and hung at Twitter's HQ.

• A Twitter staffer shared an image of the office decorations earlier this week.

• "Next I'm buying Coca-Cola to put the cocaine back in," Musk said in the tweet.

One of Elon Musk's jokes has been printed out and hung on the wall at Twitter's headquarters, according to an employee.

An image posted on Twitter Monday — with the location tagged as Twitter's main San Francisco office — shows three framed tweets displayed on a blue wall.

In the middle is Musk's tweet from April this year that said, "Next I'm buying Coca-Cola to put the cocaine back in."

That post came just two days after Musk first agreed to a $44 billion acquisition of Twitter, which took a further six months because of a series of setbacks, including Musk attempting to cancel the deal.

Musk's remark has some historical basis, with the "Coca" part of the brand referring to the coca leaves the drink was originally made with — the same plant from which the narcotic is extracted.

A 1988 New York Times article said the first Coca-Cola brewed in 1886 was advertised as a "brain tonic and intellectual beverage." The cocaine was removed in the early 1900s.

Musk wasn't the first person to poke fun at this. A search of tweets from the day before his post showed numerous users suggested he buy Coca-Cola to reintroduce the drug.

There were even fake Musk tweets photoshopped before the real Musk tweeted the gag himself.

But the world's richest person appears to find it particularly funny — because it's now said to be framed on his office walls.

On Monday morning, Musk hinted at his love for caffeine-free Diet Coke, posting an image of what he said was his bedside table, which had four cans for the drink on it.

The framed tweets were shared by a senior engineer at Twitter whose LinkedIn profile appeared to confirm his employment status.