Crazy Cat
Disclamer: I do not own any of this, except for the idea.
Dr. Takumi Usui had brought home a Nepeta catara, otherwise known as Catnip, from work, seeing as he was doing further studies and research on it's properties in medical useage. He had originally set it in the window in the kitchen with the other herbs he had growing there. Which quickly ended up with Takumi having to move the Catnip plant to his study office, and even having to lock it into a glass cupboard, because Licht had found it, licked, rolled around in it, and even eaten some, as well as even finding his way to it. Then proceeded to run all over the house, and then tired from all the excitement flopped on the floor to sleep it off.
As funny as it was, Takumi was freaking out for a bit, because he was alarmed by Licht's reaction. Especially because he doted and even spoiled Licht, in the 14 years he's had him. He's soon realized Licht was fine, with Misaki calming him down about it. (Sometimes Misaki questioned whether his love for the cat rivaled to that for her. Even though she knew it was equal. Licht proved to be a great stress relief. And watching Takumi play and cuddle with Licht was adorably cute.)
In the end, Takumi ended up taking the plant back to work, because Licht, being a smart cat, had figured out how to get into the study, and even undo to lock to get to the plant.