Curtain call question

Since the Met preserves the venerable tradition of curtain calls act-by-act in front of the curtain -- instead of the lame Broadway style where everyone comes out lamely under a lamely raised curtain and bows lamely on the lamely illuminated lame final set -- a question sometimes come up with special acuteness w/r/t Act II of SIEGFRIED (it could come up with B'way style curtain calls too -- did I mention that these are lame? -- but the Met style highlights it): should singers of unseen characters take bow?

My answer is yes: the soprano who sings for Forest Bird and the bass who sings Fafner the Dragon have legitimately sung important roles. As long as they're willing to put on something better than rehearsal clothes for the purpose, they should take a bow.

The consensus answer, however, has been no. I have never seen a Forest Bird or a SIEGFRIED Fafner get a curtain call (tho' I assume it's different in those productions, like Chereau's, where the Dragon turns back into his rightful form as a giant after Siegfried skewers him).

Some say: no costume, no bow. I say that's silly -- but if you insist, OK, let the soprano carry out some feathers and a beak with her, and maybe the bass can drag the giant-crab contraption after him on a leash. Seriously, though, why (tomorrow night) can't Lisette Oropesa and Sir John Tomlinson take bows in presentable non-costume clothing?

I ask because -- and here's the point -- Sir John wants to, and means to.

I could tell you how I know this, but then I'd have to kill you. Or not, but I'd just as soon you worried about it.