When Charles sees the bequeathed Carriage Company wagon in the family name, the nameplate reads: "Ingall's Carriage Company". Punctuation-wise, the apostrophe is misplaced, indicating one Ingall. Since "Ingalls" is the family name, the plate should have therefore read either Ingalls' or Ingalls's.
Caroline wouldn't give Charles the trunk because it was a birthday present. He said, "My birthday is not for 3 weeks!" 3 weeks prior to his birthday (January 10) would be Christmas, so she should have given it to him as a Christmas gift.
Charles says that Caroline's birthday isn't for another three months. Though this is a factual mistake regarding the real life Ingalls, the reality is that the actors, Michael Landon and Karen Grassle had birthdays that were closer to this reality: Landon on October 31, Grassle on February 25.