A painting of the former president was revealed to have a subtle reference to the Monica Lewinsky sex scandal

A portrait of President Bill Clinton – currently in rotation at the National Portrait Gallery in Washington D.C. – contains a subtle low-blow to the former head of state.

A dress-shaped shadow, barely noticeable in the painting’s background, is in fact an allusion to the “literal shadow” that the Monica Lewinsky scandal cast on Clinton’s legacy, according to the painter.

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Renowned portrait artist Nelson Shanks – who’s worked with everyone from Ronald Reagan to Princess Diana – painted the 42nd president at a New York City studio in 2005.

In order to give the effect that the portrait was actually painted in the Oval Office, the artist constructed a replica of the iconic room in his Philadelphia studio for background reference.

Initially, Shanks says he added the shadow for technical reasons: “You see that mantelpiece painted on the left? I had to do something to break up that line,” he explains to PEOPLE.

The artist chose to cast a shadow using a spare mannequin, and when he checked his closet for something to drape over the dummy, “it just so happened that there was a blue dress hanging there,” he says.

The dress immediately reminded Shanks of the infamous blue dress from the Lewinsky sex scandal. “I kind of chuckled and put the blue dress on [the mannequin], and it created a perfect shadow,” he says.

“Let’s face it, that’s a metaphor,” the artist tells PEOPLE, adding, “There’s a major shadow across [Clinton’s] presidency. And I never publicized it until the other day when I opened my big mouth” in an interview with Philadelphia Daily News

“There’s some humor attached to it,” Shanks admits. “But I hope it’s deeper than that. I hope it’s reflective of history and an anecdote that history should respect and know about at the same time.”

Not only was Shanks’ subtle allusion unknown to the general public (and the Clintons), it also came as a surprise to the prestigious National Portrait Gallery.

However, despite reports to the contrary, “No one (including the Clintons) have asked us to remove the portrait from the gallery,” a spokeswoman for the N.P.G. tells PEOPLE.