Cornetto?
The films Pegg and Wright have made together have been nicknamed the cornetto trilogy, as a character asks for a different flavour Cornetto in each; their third film will also have a character getting a Cornetto at some point.
Ah. Thanks 
It's a green mint one according to Wikipedia
The Cornetto colour also references the films: Red - Blood and Blue - Police
This is a totally artistic decision and is nothing to do with a sponsorship from Walls...
More to the point, did Pegg actually use the term 'fall'? If so, he needs a good hard slap.
IIRC Fall is the original British English term for Autumn. It was in common use in England up until the 17th century; after which Autumn became the preferred nomenclature for the season.
So, we've two options: either Simon Pegg is 500 years old and some kind of witch, or he's spent too long with Americans.