The pair have teamed up for a new song about UFOs for the British star's upcoming swing album and the Canadian crooner - whose wife Luisana Lopilato is expecting their first child - says they hit it off straight away because they are so similar.
He told Australia's Herald Sun newspaper: ''I don't think there's anyone in my life, at this point, who I could relate to the way I could with Robbie.
''We're around the same age, we've gone through a lot of the same things. He's just become a dad, I'm just about to. We both have problems, we both probably go too far with things we do. He just talks about it more than I do.''
''It's catchy and fun, neo-swing. One of the lyrics is 'Soda pop, Yoda what?' Robbie wrote it when looking at UFOs.''
Though they got on well, Robbie - who has six-month-old daughter Theodora 'Teddy' Rose with wife Ayda Field - admitted he was in awe of his duet partner.
He told RTE.ie: ''Me and Michael on the same record, I'm so excited. We're going to record a song I've written and graciously he thinks it's a good tune too and wants to be on it and I am a big-fan girl of him.
''He's quite a presence. I'm a pop star, I've got a 'character' and a 'personality' and all that but when he comes into the studio I stand back and just enjoy him being him.''
Robbie will have to get used to Michael's presence as the 'Haven't Met You Yet' star is keen to work with him again.
Michael added: ''I really like him. He's a really real, nice, insecure, beautiful guy. I hope I'm like that. Meeting guys like that, it's really cool. Any excuse to work with him more I'll take.
''He isn't making a swing record because he thinks it's gonna sell records, he's making it because he passionately loves it. He was like a kid in front of the big band. It was awesome.''