Complex sentence: Jack first appeared in Season 6, and has also appeared in "Season 12", "The Great Discovery" and "King of the Railway" and "Sodor's Legend of the Lost Treasure".
Split into simpler sentences: Jack first appeared in Season 6, and has also appeared in "Season 12", "The Great Discovery" and "King of the Railway". He will appear in "Sodor's Legend of the Lost Treasure".