Continuity mistake: When Ferg sets Walt's boots down, the right one tips over. But in the close up shot of Walt putting on the left boot, the right one is standing back up. But in the next shot you can't see it (if it was still standing it would be in the shot) and then we see Walt finish putting on his left boot, the right boot is back to being tipped over.
Factual error: We see Donna's driver's license, the expiration date is wrong. Driver's licenses expire on the person's birthday, not the issue date. Plus, in Wyoming they're valid for 4 years and hers is only valid for 3 years.
Answer: Something he made up.