I've a theory about flubbing the names, because it is happening in my head with New Girl, though not out loud yet. When we think of our "special person" and the emotion it triggers, it is automatically translated to a first name. For the longest time, your brain translated "special person" to "Mr Fantastic". Now, you're starting to hit that "special person" button again, after a long time of not using it, and your brain is still wired to translate it to the wrong person. But it's a good sign for your Guy that you're hitting that button. It means he's becoming to you, to your heart and your brain, who Mr Fantastic used to be. He's becoming your "special person".
I've used the name of my first girlfriend (of 5 years) for a decade after we split up. Heck, it still happens once a year. It's just that she occupied this place for a long time, so the wiring with her name is strong. It's not that I think about her. When it happens again, because it will, don't make a big deal out of it, don't suggest by your reaction that he should be offended. I bet he won't be. I wouldn't be if my girlfriend used the wrong name.
Happy birthday!
M39 D6 D3 (at S) S 2014-09 D 2016-09
"You can't start a fire sitting around, crying over a broken heart" - Bruce Springsteen.