Some developers of the show put their names in some backgrounds as hidden:
"Coffee by Alex" ad from "Shell Game"
Alex Kirwan - art director.
Painted "Jolt" from "The great unwashed"
This is more complex. "J" is for Joseph, "olt" is for Holt.
Joseph Holt - background designer.
"Kirwan's" truck ad from "Call hating"
Alex Kirwan again.
Some time ago, I saw a similiar thing:
This is from Mortal Kombat 3 background.
The "Boon/Tobias" sign.
"Boon" is for Ed Boon and
"Tobias" is for John Tobias - MK game creators.
They don't wait for the final credits at least!