Punch and Judy (AKA Adam and Lilith) have, but it’s surprising, and taken as a testament to Gil’s skill in putting them back together. Then again, when Klaus constructed himself (presumably he’s the one who did it), he took special care in this matter.
And even if only Jägers ordinarily go to Mama’s secret bar, Higgs is certainly not ordinary (nor, for that matter, is Zeetha). Old Man Death the sandwich-maker is probably welcome at the secret bar, too, though I don’t know if he’s ever chosen to go there.
Yes. We have canonical(as in, it’s appeared in the main comic), unequivocal evidence in the form of Adam and Lilith Clay’s daughter.
I’m not sure if a spark working on themselves would then come to be called a construct. Then again, maybe they would. But in this case, I read somewhere that Klaus was put together by his parents from the remains of three Wulfenbach children after a lab accident or something.
ETA: cite
http://www.reddit.com/r/IAmA/comments/1fcxje/we_are_kaja_and_phil_foglio_creators_of_girl/ca92zci
I think the latest comic is evidence supporting the idea that Higgs is NOT a Jager.
No, I still think he is. He’s just not as schmott as Gil, and so it takes him longer to realize the implications of all this sparky madboy time stuff (beyond the obvious fact that it’s a Really Bad Idea).
He might not be as schmott as Gil, but I believe it is established that he is much older and far more experienced. He clearly was a Heterodyne or a Heterodyne retainer before attaching himself to the Wulfenbachs, and has probably seen far more madboy shenanigans that Gil could imagine. He’s a little jaded by now, but is doing what he can to preserve the Wulfenbach family line.
I was referring to the aging of Vole, which confirms that Jagers grow(and grow more monstrous) as they age. And we know Higgs is really old.
But, if he is a Jager, he is one atypical in physical appearance.
Yes, but it isn’t just physical appearance anymore, now the difference is also physiological(he doesn’t grow larger as he ages). I think this is additional evidence against the theory. He could still be a Jager who doesn’t look like a Jager, talk like a Jager, age like a Jager, or behave like a Jager(he doesn’t enjoy fighting). But if it’s true, then I think it’s at least fair to say we’re not expected to figure it out from what we know about the world.
I’ve just caught up to the latest strip. There’s one panel in particular that may have bearing on this. Gil asks Higgs why anyone would drink the Jagerdraught. Higgs makes some kind of face and replies “I dunno”.
It’s kinda hard to tell but that look could be " Gee, the stupid things I did when I was young" look. 
While we’re asking esoteric GG questions – The castle – male or female? Possibly as a result of playing Portal, I’ve always imagined the castle as a Glados-type female. Which seems to go well with its casually homicidal nature. But I’m not sure there’s any internal evidence one way or another.
I don’t think clanks are particularly gendered.
Eh? Many of the more sophisticated clanks have been. Certainly the muses were. The enormous clank guarding the school was Mr. Tock. The Castle definitely has a personality, so at least the voice might be gendered.
Further evidence for my hypothesis that Higgs is a perfected Jager, not the ur-Jager.
Where’s the evidence that the Heterodynes were trying to ‘perfect’ Jagers? Is there any reference that there were multiple types of Jagerdraughts? Or later ‘improved’ Jagers? Or is Higgs your evidence for that? In which case, you’re begging the question a little.
The evidence is the variability of the effects of the Jagerdraught on the Jagers. Obviously, the Heterodynes were tinkering with the formula. And when a Spark tinkers, the end product gets better.
Yeah, not a lot of evidence for my “perfected Jager” hypothesis, but there is not evidence working against it either (unlike the the ur-Jager hypothesis).
I think it’s more likely that the draught was the same, it just has inconsistent effects.
This is my view too. We already know it affects different subjects differently - very few make it out alive.
Shoots revivification ray at desiccated husk of a thread.
There is now official word: Mr Higgs confesses he is a Jager and the Spymaster to Agatha Heterodyne.