The Fishin' Party
Dialect spelling
Riley writes in Hoosier dialect—Indiana rural speech. 'Wunst' (once), 'crick' (creek), 'ist' (just). This is a child narrator's voice, not Riley's own.
The warning
The adults know something the kid doesn't yet—this creek is dangerous for small children. Sets up the tension between child's excitement and parents' reluctance.
Fishing silence rule
Pa's exaggerated insistence on silence ('ef you talk, er say / Anything, er sneeze, er play') suggests he's making excuses for not catching fish. The kid believes him completely.
The store-bought fish
Ma buys a fish to save face after the failed fishing trip. 'Now she'll have a fish for shore' shows her determination to salvage something from the day.
Pa's humiliation
Pa won't eat the fish because it's proof he failed. When the kid chokes—probably laughing at the irony—Pa hits him to shut him up. The appeal to Ma is the punchline.