The Family Upstairs

The Family Upstairs was an early comic strip by George Herriman. The titular "family upstairs" is never seen; the audience only sees the (usually angry) reactions of the inhabitants of the apartment below them to the annoying noises, escaped pets, and so on. It is chiefly notable for a tiny companion strip that ran alongside it that featured a couple of characters that later became much more well-known.

Scans of (some of?) the strips are online at the Ignatz Archives.

Tropes used in The Family Upstairs include:

Animal Jingoism: One series of strips, narrated by Ignatz, goes into the history of mouse/kat rivalry--it seems that the Golden Age of Mice came to an abrupt halt as soon as a kat arrived on shore and started eating all the citizens. Therefore, "Ignatz the Avenger", as he styles himself, holds that Krazy deserves every brick he gets.
Anthropomorphic Shift: As the Dingbat's rather ordinary-looking pet "kat" gradually evolved into Krazy, it began to walk on its hind legs.
Funny Background Event: Plenty--most famously, the one that became the entire premise of Krazy Kat.
Breakout Character: Two--Krazy and Ignatz.
The Ghost: The entire "family upstairs" is made up of these. Despite their lack of presence, they cause a lot of trouble.
The Voice: In at least one strip, we hear the Family Upstairs cheering uproariously because the Dingbats came home from their vacation.