Corrected entry: When the Vikings first see the dragon of the north sea and mistake it for the sun, the glowing orb is quite round and clean, yet as they get closer it becomes evident that it's covered in seaweed, which should have obscured parts of it earlier.
Corrected entry: Both Loki the blacksmith's assistant and Leif the Lucky are seen to be in Valhalla when Erik arrives, however they both drowned (Loki is thrown overboard by Keitel Blacksmith and Leif falls overboard after the dragon of the north sea sneezes) and as Odin says "this place is reserved for those slain in battle".
Correction: Both fell overboard from warships and were armed at the time. They meet the Viking definition of 'slain in battle'.
Correction: If the light from the dragon is bright enough, you would not see the seaweed covering it. There are thousands of sunspots from the sun, but we don't see them with the naked eye, and the sun appears to be a round sphere, when in fact it's shape shifts a little.