Ray Winstone shows up driving a tractor in the Series 3 episode "Manure".
Name's the Same: Lampshaded in the first episode; Howard Hughes shares his name with the eccentric tycoon, and another Close resident, Tommy Cooper, shares his name with a popular stage magician and comedian. Paul finds the names much funnier than Martin finds them.
Throw It In: Most of the times when Paul is trying not to laugh at Martin's antics, it is real. It started as unintentional but they kept it because it adds depth to the characters' relationship.