Tiny Toon Adventures/Montana Max's Mansion

As Furball
Climb quickly up the right wall. The cannons on the right will fire too soon, the ones on the left too late, and you will reach the the top with no effort.

As others
The fish cannons on the sides:
 * Only fire once
 * Those on the right will shoot over you if you crouch on the elevator
 * Those on the left will require jumping

Crouch on the elevator and completely ignore the cannons on the right. Time your jumps based on left-hand cannons — jump up at the exact moment that the cannon's bottom edge aligns with the top of your crouching character. Jump height should be around 1/3 of maximum. Don't forget to keep holding so that you crouch again the moment you land back on the elevator.