If there's one thing comedians do not find funny, it's joke thieves.

SNL's Pete Davidson has lashed out at comedienne Natasha Leggero after accusing her of stealing one of his gags on a late night improv comedy TV show.

Davidson was even more incensed as Leggero was present at Justin Bieber's Roast on Comedy Comedy Central when he made the wisecrack, which was aimed fellow comedian Jeff Ross.

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Thief?: Natasha Leggero, left, was slammed by SNL' Pete Davidson on Twitter on Sunday after he accused he of stealing one of his jokes on @Midnight

On Thursday's episode of @Midnight, where Leggero and Ross were contestants, host Chris Hardwick asked the guests to air some of their barbs at Justin Bieber that they didn't get a chance to during the Roast, which was recorded earlier this month.

But Leggero instead took aim at Ross, claiming 'Jeff Ross looks like someone put a butter sculpture of Mr. Clean in the microwave'.

During Bieber's Roast, Davidson had told Ross 'You look like someone put Seth Rogen in the microwave'.

Original: 21-year-old Davidson, the youngest member of Saturday Night Live's current cast, made the joke about fellow comedian Jeff Ross during Justin Bieber's Comedy Central Roast

On Sunday the 21-year-old, who is Saturday Night Live's current youngest cast member and first ever to be born in the 90s, called Leggero out on Twitter.

'@natashaleggero how the f**k u gonna do a joke on @midnight that I did on the Bieber roast that we were on together?,' he wrote.

The 41-year-old immediately apologised, claiming she forgot about Davidson's insult made weeks earlier.

Second-hand?: Leggero said Ross looked like 'someone put a butter sculpture of Mr. Clean in the microwave'

Which is it?: Davidson had already observed earlier that month - in Leggero's presence - that Ross looked like 'someone put Seth Rogen in the microwave'

'@petedavidson @midnight OMG so sorry I would never intentionally steal your joke- we had similar jokes and I forgot about yours,' she replied via tweet.

However both tweets were deleted shortly afterward.

Curiously - since the theme of @midnight is improv comedy and thinking on one's feet - Ross didn't immediately pick up on the fact Leggero had just hit him with a second-hand barb, proving he either didn't realise or he didn't think the jokes were that similar after all.

Tasty: Bieber's Roast - which all three comedians took part in - is due to air on Monday night on Comedy Central

Davidson attacked Leggero on Twitter on Sunday Tweeting: 'how the f**k u gonna do a joke on @midnight that I did on the Bieber roast that we were on together?'

Meanwhile Ross himself was in a different kettle of hot water for jokes made at Justin Bieber's Roast, which is to be broadcast on Monday night.

He felt a heavy backlash when he made a joke about the late Paul Walker, who's Furious 7 co-star Ludacris was also a roaster on the night

Parodying the rapper's lyrics, he said '"Move, b***h, get out of the way", is what Paul Walker should have told that tree', prompting outrage from fans of the actor, who died in a car crash in November 2013.

The offending joke has reportedly been edited out of the broadcast.

Sorry: Leggero immediately apologised Tweeting: OMG so sorry I would never intentionally steal your joke- we had similar jokes and I forgot about yours'