The British actor - who wrote the sci-fi comedy script with long-term friend and collaborator Nick Frost - enjoyed a "masochistic" moment with the iconic `Alien` actress, and admits getting her involved in the project was like having "the queen" on set.
Speaking at the movie`s world premiere at the Empire cinema on London`s Leicester Square, Simon told BANG Showbiz: "Have her pick me up was like a dream come true - in a masochistic way.
"She came on to the set and it was like the queen was coming to visit. She was lovely and of course incredibly down to earth."
The movie tells the story of two comic book geeks who go on a road trip across the US and come across an alien - voiced by Seth Rogen - outside of famed military zone Area 51, and Simon admits the journey taken was first thought of as a way to get a free holiday from the movie studio.
He joked: "We laughed a lot. We did the road trip initially as a way of getting a free holiday out of Universal.
"Of course it ended up being a very inspiring time and a lot of what happened on that trip fed into our script."
Simon was joined on the special purple carpet at the premiere by co-writer Nick Frost and stars Sigourney Weaver and Jason Bateman.
Coldplay singer Chris Martin also put in an appearance.