Mom
Explanation
The Joke
A child is looking at their mother, who is tied up in bed. The tied-up woman shouts, "Don't believe her! I'm the real mom! You've got to untie me before it's too late." Meanwhile, from the bed, another voice says, "Don't untie her! I'm the real mom!" The caption at the bottom reads: "This is the best possible use of a long lost twin."
The Humor
The comic takes the classic dramatic trope of identical twins (or doppelgangers) where someone must figure out which one is the "real" person, and reveals that the entire scenario was engineered by a mom who found her long-lost twin and immediately realized the best use for this situation: getting to stay in bed. One of the "moms" — presumably the real one — has tied up her twin and is using the confusion to avoid parental responsibilities while remaining comfortably in bed.
The humor comes from the subversion of expectations. The setup looks like a thriller or horror scenario (someone tied up, desperate pleas, an impostor), but the punchline reveals it's just an exhausted parent who found an elaborate way to sleep in. The "best possible use of a long lost twin" turns out to be neither dramatic nor sinister — it's delegating childcare.
Broader Context
SMBC often explores the reality of parenting through absurdist scenarios. The joke taps into the universal experience of parental exhaustion and the fantasy of having someone else handle the kids. The twin/impostor trope is a staple of fiction from Shakespeare to soap operas, and the comic deflates all that dramatic potential by using it for the most mundane possible purpose: getting a nap.