>>527616194
It'd have to be done very carefully to not come across as corny.
>Happens only via some immense file fuckery in the final game
>Maybe also requiring things like the Eggs, Shadow Crystals or some other obscure requirement
>Could even need to be in a specific spot
>True Lab style build-up where you don't see him for a lot of it with a decent selection of lore-dump-ish readouts or files to do with Gaster, finally revealing what the hell his deal is.
>Different devices, experiments, glass tubes and/or vessels, etc.
>When you actually see him it's a relatively short moment of interaction.
>Maintains his aura of mystery of where/what he'll do next while giving the player an understanding of what his intentions and methods are.
Straight up having him appearing without any sort of mystique like
>"I'M WING GASTER, THE ROYAL SCIENTIST!"
would totally shit the bed