Continuity mistake: When Ritchie, Eddie, Spudgun and Dave Hedgehog enter the pub with the fake money and order drinks, Ritchie asks for Absinthe but is told that the pub doesn't have any and is given Pernod instead. Later, when the £5000 pub quiz poster is pointed out, Ritchie says he's had half a pint of Absinthe and can't see anything. Where did the Absinthe come from if the pub didn't have any earlier in the episode and they never left?
Revealing mistake: During a few of the "flaming fart" scenes, you can see a wire connected to the bottom of the actors. It's hard to see because it appears that it was attached to their legs in some way, but you can still see it when they move around a lot. The easiest place to see it is when the "devil" knocks on the door and they all fart and jump around, look carefully between/to the side of eddies legs for a black wire. It's not the dressing gown belt because that's tied around their waists.
Character mistake: Eddie, Spudgun and Dave Hedgehog all appear worried at the fact that the devil takes "virgin's blood." However, it is apparent later in the episode that the 'devil' is in fact Dave Hedgehog's daughter, meaning he isn't a virgin.