So it turns out it wasn't all a dream: two people who have been dating for less than a month really are engaged to be married and commit to each other for the rest of their lives.
That's not to say it's not a publicity stunt, of course - if you'll excuse our cold, cynical hearts for a moment. There's a bang of Hiddleswift off this, if you ask us.
Fallon joked: "You know you didn't have to get engaged to Ariana Grande to come on our show?" to which he replied: "But I did, though!". He added: "I feel like I won a f**king contest" and joked that men were tipping their hats to him walking down the street.
Watch the full thing below:
— Fallon Tonight (@FallonTonight) June 20, 2018