No grappling hook necessary!
Cat Climbs Open Stairs From Underneath

Because doing things the hard way is the story of my life, this is a video of appropriately named Ninja Cat climbing a flight of open stairs from underneath. Apparently Ninja Cat does this all the time, but this was the first time his caretakers were able to document it due to his stealthy, unpredictable behavior. I assume they named him Ninja Cat after realizing his Shinobi tendencies, because you would never guess he’s a ninja just by looking at him. Which, OMG — is exactly what a ninja would want you to think! Wow wow wow, Ninja Cat: 1, Me: D-