Which sounds quite arrogant and presumptuous that you know what I and my players want more than we do.
The hypothetical example only comes up because someone in your group wants to play a turtlechap. The assumption is therefore that they are known to you and already on board with your game's premise and lore etc, they just want to add something to it, and presumably (if they are as familiar with the lore as you say) they have an idea of how it could be explained. It's an assumption that the player is acting in good faith.
I agree that if random strangers approach you in the street and shout 'Tortleman?' you should keep walking.


