It's an immutable law of comedy—under no circumstances may a comic use another performer's material. Naturally, with so many comics making observations about the world around them, similarities are bound to exist between one guy's airplane food joke and another's. Allegations of joke lifting are common, with top-tier talent like Conan O'Brien and Amy Schumer often having accusations thrown their way (Schumer, for her part, vehemently denies any thievery). But throughout standup's history, some similarities have been too close to ignore.

1. MILTON BERLE

The late, great star of stage, screen, radio and TV was once the nation's most popular comedian, earning him a 30-year television contract with NBC and the endearing nickname Uncle Miltie.

But to many of his fellow performers, Berle became known by the much less affectionate nickname "The Thief of Bad Gag" for his legendary penchant for joke lifting. Fellow legend and occasional enemy Bob Hope once remarked that Berle "never heard a joke he didn't steal." In another instance, Jack Benny defended his own practice of using Berle's material by saying: "When you take a joke away from Milton Berle, it's not stealing, it's repossessing."

Unlike many other accused bit-thieves, Berle never went out of his way to dispel the reputation, once joking to Larry King: "I don't steal people's jokes. I just find them before they're lost."

2. CARLOS MENCIA

The former star of Comedy Central's Mind of Mencia has been accused of plagiarism by everyone from George Lopez—who once claimed he roughed-up Mencia over a supposedly stolen set—to South Park. However, the most famous example was shared with the world thanks to a viral video posted by comedian Joe Rogan. In the footage, Rogan is shown running onstage to confront Mencia during a 2007 performance at the Comedy Store in L.A. Among other, more colorful names, Rogan refers to Mencia as "Men-Steal-ia."

3. DANE COOK

Dane Cook reached the pinnacle of stand-up comedy success in 2005 when his album Retaliation went all the way to #4 on the Billboard chart. Sold-out large-arena gigs, movie flops, and tabloid coverage quickly followed—and all served to fuel a rabid anti-Dane movement within the comedy world. With that came an intense microscope on Cook's material and, predictably, a rash of joke swiping charges. The most well-known example includes a Cook bit that bears a suspicious resemblance to an earlier one by Louis C.K.—one of the most revered comics working today. Although compilations seem to confirm that Cook has used at least three of his bits, Louis C.K. has mostly downplayed it—"I'm not going to do anything about this. I'm not going to court over a bit called 'Itchy A**hole,'" he once joked. Just for good measure and consistency, Joe Rogan has also accused Cook of lifting jokes.

4. ROBIN WILLIAMS

Long before he was an Oscar winner, Robin Williams was known to comics as a major material thief. He was even alleged to have used other comedians' material on Johnny Carson's Tonight Show. One well-traveled anecdote claims that when fellow comics spotted Williams in the audience of a comedy club, they would immediately stop their act to prevent him from writing down their best jokes. According to Richard Zoglin's book Comedy at the Edge, David Brenner once asked Williams' agent to "Tell Robin if he ever takes one more line from me, I'll rip his leg off and shove it up his [bleep]!" Williams discussed his younger days in comedy and of not understanding the consequences of borrowing material with Marc Maron in 2010; he once playfully referred to the practice as "joke sampling."

5. JAY MOHR

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The former host of Last Comic Standing is an admitted comedy plagiarist. In his 2004 book Gasping For Airtime, which recounts his tumultuous two-season stint on Saturday Night Live, Mohr details an infamous incident in which he took a New York comedian's joke and turned it into a sketch. NBC was forced to settle with the joke's originator, but Mohr himself escaped any serious repercussions.

6. DENIS LEARY

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The former star of Rescue Me has been accused of stealing not only some material but his entire stage persona from the late cult comic Bill Hicks. He's also been accused of lifting material from former stand-up and Hollywood heavyweight Judd Apatow and Louis C.K. But Hicks himself, who was close friends with Leary, severed his friendship with him over the number of lifted jokes used on Leary's No Cure for Cancer album. "I have a scoop for you. I stole his act," Hicks joked with Austin Comedy News in 1993. "I camouflaged it with punchlines, and to really throw people off, I did it before he did." Hicks passed away from cancer the following year.

This piece originally ran in 2010.