Kayvan Novak practiced the impersonations of his co-stars by running through the lines with them as well as studying recordings they provided in order to get a sense of their rhythms. Novak also admitted in an interview with Newsweek that he'd even practiced the voice of Matt Berry in the shower to get it right.
The song Laslo sings to Meg when disguised as Nandor is Peg by Steely Dan.
When the guide first shows the gang the cloak of duplication, a set of Kings Guards white cloak Armour from Game of thrones can be seen just to the left side of it.
When the vampires are getting measured for their robes, on the background, behind the Guide, there is a picture of the original cast from the movie 'What We Do in The Shadows'.