Does Death's Head remember the Transformers after crossing over into the Marvel universe? Does he/any characters he interacts with mention or reference the Transformers at all? Comic-heads, let me know!
Off the top of my head, DH alludes to the events of "Legacy of Unicron" when he first meets the Doctor, and then there are some mentions of the "robot universe" he used to live in, when "The Incomplete Death's Head" recapped his history. They don't talk about 'em in any detail, but there's no particular reason to think DH doesn't remember them. The Death's Head who's been appearing in Marvel Comics over the last decade, though, is apparently from a point in time BEFORE ever going to the Transformers universe.
Interesting... Having modern DH come from before he encountered the Transformers makes sense since it means Marvel doesn't have to worry about any past events they can't reference.
They can reference them, same as Spidey being used in other publisher's G1 comics reprints instead of being replaced with generic webman like they recently did with the Invincible animated series. It's just something they'd need to OK first, and even if they didn't get the OK they could just mention giant robots that turned into trucks and stuff, but as you say it's more convenient to sidestep it completely, especially for modern no fun Marvel.
There are only a few occasions I can think of other than those Chris has already mentioned. Firstly, in Marvel Bumper Comic #5 there was a 1-page house Ad using artwork from Death's Head #1. In this he monologues about fighting Galvatron and Doctor Who (fun fact - I believe that this is the only time both the Transformers and the Doctor are explicitly named in the same place in any Marvel comic). Secondly, in X-Men '92 #9, a Celestial, Xodus The Forgotten, is materialising in the atmosphere to general panic. Death's head is unconcerned and demands his fee from Lila Cheney points out "the giant planet killer in the sky" and, presumably referencing Unicron, DH says "I've seen bigger".
