I think you are referring to a construction found online in which a characterization is presented in one word followed by the word much, read as a rhetorical question and intended as a criticism. It is not intended or imagined to be grammatically correct.

"Excited much?" would be "Do you get (this) excited often?" and is intended to paint the subject's enthusiasm as unwarranted and to suggest that it reflects on or represents the subject's general character.

"Stalker much?" is an attempt to portray behavior as stalker-like and would be grammatically written "Do you often behave like a stalker?"

I think you are referring to a construction in which a characterization is presented in one word followed by the word much, read as a rhetorical question and intended as a criticism. It is not intended or imagined to be grammatically correct.

"Excited much?" would be "Do you get (this) excited often?" and is intended to paint the subject's enthusiasm as unwarranted and to suggest that it reflects on or represents the subject's general character.

"Stalker much?" is an attempt to portray behavior as stalker-like and would be grammatically written "Do you often behave like a stalker?"