Meet VertiGo: a wall-climbing robot that can transition from the ground to the wall with its two tilting propellers. It also has 4 wheels, with a pair that is steerable. The robot is designed to travel through indoor environments with agility. As it is explained on Disney Research’s page:
The use of propellers to provide thrust onto the wall ensures that the robot is able to traverse over indentations such as masonry. The choice of two propellers rather than one enables a floor-to-wall transition – thrust is applied both towards the wall using the rear propeller, and in an upward direction using the front propeller, resulting in a flip onto the wall.
You can find the complete paper on the robot here.