battle
Explanation
In this comic, a parent is tucking children into bunk beds and telling them that "Daddy and I are going to lock the doors tonight and fight monsters." The parent explains that the monsters are "evil doppelgangers that sound exactly like us" but reassures the kids that the monsters "are losing."
The caption below reads: "I never found out why they needed the neighbors to help, but I was proud to live in a strong community."
The joke is that the "fighting monsters" is a euphemism the parents are using to explain away the loud noises the children will hear that night — the parents are actually having sex. The "evil doppelgangers that sound exactly like us" explains why the kids might hear voices that sound like their parents making unusual noises. The detail that the monsters "are losing" explains why the sounds might be enthusiastic or triumphant. The punchline about needing "the neighbors to help" implies that the parents eventually expanded to group activities, which the naive child narrator interprets innocently as a strong community coming together to fight monsters.
The humor comes from the dramatic irony of the child's innocent narration contrasted with what the adult reader understands is actually happening. It also plays on the common parenting challenge of explaining away adult activities to curious children, taken to an absurd extreme where the cover story has to keep expanding to account for increasingly hard-to-explain circumstances.