Space guns, fighting monsters, and fighting other dogs.

There are moments where swear words are cut out or replaced by barking (euphemism), but this could be a false memory.

One use of "suck" in the third episode of Season 1.

There is a brief reference to an alcohol-like substance.

There are battles, references to hating humans/humans destroying the Earth/wiping out humans, arguments, feelings of despair, and general dark elements scattered throughout the series.