Am I a joke to you?

Ashtrap sounds way better than Dark Springtrap... Why couldn't they use that?

Wait, there's a Dark Springtrap?

The one from the Sister Location cutscene showing him still going after the Fazbear's Fright fire is called Dark Springtrap. In a whole line where the names are "*insert word*-trap", they just slap "Dark" onto Springtrap.

Is that from the last cutscene from Sister Location's Custom Night, or no?

Yep

Ah, now I know what you're talking about. I watched Markiplier play it before, right when the Sister Location burnt to a crisp and, yet again, Springtrap rises from the rubble to kill again.