Getting Clasko: (I hope I get this right) Go to Mushroom Rock Road, and head towards the red arrow. There, Yaibal and Clasko and some Youth League cadets will greet you. Inside, complete the mission "Foggy Fiend Frenzy" (at least I think that's the name). Return to the Celsius then go back to Mushroom Rock Road. Head a little down-right from the save sphere to see Clasko near the edge. Welcome him aboard the Celsius now. Afterwards, go check on him in the Cabin.