For a cocktail party in 2009, he tested the theory that time travelers existed by only inviting the guests after the party ended.
Now it seems time travelers are invited to Hawking's memorial service, which takes place on June 15 at Westminster Abbey in London, where his ashes will be placed next to Isaac Newton's resting place.
Those who wish to attend the service can sign up for the special event via a public ballot put out by The Stephen Hawking Foundation. Only 1,000 will be selected to be invited.
The funny thing is, in order to attend, you're required to add personal information to the form, including your birthdate. Oddly, birthdates from over 20 years into the future are included.
It's comforting to know that even after Hawking, he about the possibilities of defying time.