The pair will almost certainly overshadow the rest of the panel on Thursday night, who include conventional politicians like Labour's shadow transport secretary Mary Creagh.
What could they end up fighting over? HuffPost UK presents five questions that the comedian and activist may decide to ask the Ukip leader.
2. "How can you say Ukip isn't a 'far right party' when you have the support of so many racists?"
[Ex-City trader Farage went to Dulwich College, while his party's two MPs, Douglas Carswell and Mark Reckless, went to Charterhouse and Marlborough College respectively. Spread betting magnate Stuart Wheeler, an Old Etonian, also decided to support Ukip as its treasurer. Meanwhile, Ukip donor Paul Sykes is one of Britain's wealthiest men with an estimated £650m in the bank.]
4. "Is Ukip really different or is it just a 'modest amplification of the prevailing political mentality'?"
[Not only was Farage once part of the Conservatives, but his two MPs left are former Tories, as are his vice-chairman Neil Hamilton, current MEPs Roger Helmer and William Dartmouth, and current peers Lord Pearson and Willoughby de Broke.]
5. "Why don't you drop the erroneous belief that immigration negatively impacts on people's lives and go after tax dodgers? You like paying your taxes, don't you?"
[Farage, who previously railed against "rich people and successful companies" not paying their fair share, was reported to have funneled earnings into a company which would mean he pays 20% corporation tax on profits of £45,000, rather than 40% income tax.]