Mrs Oleson's red dress with green insert is made of the same floral calico fabric as the dress Laura wore to her first teaching job.
The fluffy white plant that is in the pond and that Nancy wants looks like Pampas grass. It doesn't grow in just water.
The cigar box that Willie swaps with Nancy's says Joya De Nicaragua on it. However, Joya De Nicaragua was not established until 1968.
The floral porcelain piggy bank that Nancy smashed was made by the Lefton company in the 1950s.
Pampas grass is native to California and the Mojave desert. It does not grow in Minnesota.
Elmer's brother appears to be school age. No explanation is given for why he doesn't attend with Elmer.
Since Laura used to actually go hunting for "creatures" her reaction to Nancy's project is questionable at best.
Champion tomboy Laura who catches bullfrogs with her bare hands would never have asked her brother to pick up a baby garter snake off her desk.
Writer Chris Abbott did not know Laura's character at all. She would NEVER have just sat there mute when one of her students quit school and ran out.