So’s your old man!

so's your old man

dated A childish, petty response to an insult, essentially meaning "same to you." "Old man" refers to one's father. A: "You're a stupid monkey brain!" B: "Oh yeah? Well, so's your old man!"
See also: man, old
Farlex Dictionary of Idioms.

So’s your old man!

exclam. The same to you!; Drop dead! (Indicates basic disagreement or hostility.) BILL: You’re acting like an idiot! TOM: So’s your old man! I don’t know what you said, but so’s your old man!
See also: old
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • so's your old man
  • so's your old lady
  • I know you are but what am I?
  • have (one's) monkey up
  • have your monkey up
  • pudding and tame
  • get (one's) monkey up
  • put (one's) monkey up
  • monkey business
  • have got a monkey on (one's) back