It's wrong to blame someone for something someone else did.
Homer falls asleep while on his riding mower and ruins several lawns including Peter's and Stan's.
Peter wants to find out who ruined his lawn.
Peter investigates closely at the blades of grass on his and Stan's lawn.
Peter accuses Stan of ruining his lawn because his lawn is closest.
Peter finds out the cuts match Homer mower rather than his own or Stan's.
Peter and Stan argue all day and never resolve any of the issues.