But Masa, Mune and Doreen actually became physical, thanks to Lavos' power.
Proof?
The best we've got is a quote from Doreen in Enhasa:
"The power of Lavos can make hopes and dreams come true...but at what cost?"
Mind you, I don't know if it was Lavos' power that created them, and truth be told, I'm skeptical of that position. I figure a powerful guy like Melchior, with access to tons of Dreamstone, could very well have figured that one out on his own, being the Guru of Life and all.
I think it could have happened when he was first building the Mammon Machine. Like in RD where the flame was, and most likely in CT, even a mental wish or some kind of link with it could have turned the Melchior dream trio into physical beings.
That's only in RD. In CC (
thus in CT also), the Frozen Flame never granted anyone a wish. This stuff about wishes is just a fake legend like the legend claiming that the Dragon Gods are good guys and that they sealed the Flame.
Belthasar never had a wish granted by the Flame, although he could easily have wished to save Schala without having to do all his Project Kid crap. Chronopolis itself wished to control space-time and got time-crashed instead. For all the time FATE had the Flame, she never managed to reincarnate into a new species like she wished to (Lynx doesn't count). The "Time Devoured" Dragon God also didn't ask a wish to the Flame when she brought it to Terra Tower, although god knows what crazy and gloomy stuff she could have wished. After they defeated this Dragon God, Serge, Kid, Funguy, Van, Viper, etc. also didn't ask for whatever wish they wanted.
All the FF can do is some time-space tricks like accelerating the human brain's evolution, making time crash, or reverting someone's injuries (and that last thing was only because of Schala's will).