Elrod the Viking:

Win the "Lift Tower Challenge" trophy. To do this, start the Rock Ridge freestyle course. Go left and downhill past the chairlift. Look for the stone ramp to the right. Jump to the tower and stop on it. You must now travel up to the higher tower riding on the cables. When you reach the other side, you will win the trophy.

Sal the Alien:

Win the "Find Out The Truth" trophy. To do this, start the Fox Creek freestyle course. Jump over the canyon and continue going along the side of the buildings. You should see an opening and lots of rocks. Floor it and hit the two-sided ramp. Make sure you are heading toward the buildings. Hit the ramp and aim your jump so you land on the awning covering the porch of the back of the building. Keep going and jump the next ramp, landing on the roof with the hole in it. Go past the hole and turn around - you will see another ramp. Jump this one to get to the highest roof. After you land on the roof, position yourself so that when you jump the last ramp you'll land on the rock bridge. Jump down to the ledge leading into the open mine shaft. Continue to follow this path until you reach Sal's UFO. Continue past the ship into the next room and you will see Sal and win the trophy.

Cameron Steele:

Win the "World's Longest Jump" trophy.

Superfly:

Win the "Crane's Eye View" trophy.

Bee motorcycle:

Win the "World's Highest Jump" trophy.

Cow motorcycle:

Complete the "Brave The Vertical Drop" challenge.

Fish motorcycle:

Win the "Dominate 250cc Pro Race Season" trophy.

Playa motorcycle:

Win the "Dominate 125cc Pro Race Season" trophy.

Fire motorcycle:

Win the "Dominate 250cc Pro Freestyle Season" trophy.

Tiger motorcycle:

Win the "Dominate 125cc Pro Freestyle Season" trophy.

Extra track editor barriers:

Win the "Dramatic Entrance" trophy.

Extra track editor movable objects:

Win the "Impossible Stoppie" trophy.

Extra track editor ramps:

Win the "Impossible Wheelie" trophy.

Extra track editor platforms and Station Z:

Win the "Cross Training" trophy.

Balloon toss mini-game:

Win the "Safety First" trophy.

Wheelball mini-game:

Win the "Mega Stunt" trophy.