1) The blue whale is the largest animal to have ever existed, with an average length of about 82 feet (25 meters).

2) The musical "The Phantom of the Opera" has been running in London's West End since 1986, making it the longest-running musical in history.

3) Celtic mythology encompasses the folklore and legends of the Celtic peoples across Europe, particularly in regions like Ireland, Scotland, and Wales. It features deities like Morrigan, Cernunnos, and Brigid, and delves into themes of nature, magic, and the heroic exploits of legendary figures like Cu Chulainn.

4) The Northern Lights, also known as the Aurora Borealis, are natural light displays that occur in the polar regions due to interactions between the Earth's magnetic field and solar particles.