Continuity mistake: Steve buys the ring for Laura at the end of their class project, then sells it to Carl as a gift for Harriet. Then when he proposes to Laura he says it's the same ring from that day.
Carl, Eddie, and Steve are out ice fishing. At one point Carl falls through the "ice" and you can clearly see that the "ice" is made of some sort of styrofoam. It looks like the stuff used for packaging. The snow looks just as fake.