As hilariously whimsical as the notion may sound to some, walking a kitten on a leash may not be as unpractical an idea as you think. Leash training can be a safe way for kitties to get exercise -- all while enjoying the sights and sounds of the outdoor world.
If you're at all familiar with cats, then you probably are well aware that many of them possess pretty impressive stubborn streaks. If a cat doesn't want to do something, she doesn't want to it, and nothing will really change that. Because of this resilience, you may want to start your kitten's leash training young -- think around 8 weeks of age, if possible. A young kitten may be more open to the concept of walking outdoors with a leash than a more seasoned counterpart. For a wee kitten any younger than that, the unfamiliarity of the outside world may be a little overwhelming, so try to stick to two months.
Just because it's often a lot easier to leash train a sprightly young kitten is no excuse to not try with your middle-aged or elderly pet. Once a cat is past the tender and impressionable 16-week mark, teaching her how to do new things may take more time, but is certainly not impossible. Encourage your hesitant fluff ball to take to leash training by trying to establish a "feel good" connection to it -- think yummy tuna or salmon treats, for example.
Regardless of how young a tiny kitten is or how "senior" an older cat may be, walking outdoors on a leash may be able to greatly enhance a pet's life and health, from regular physical fitness to giving him something exciting to look forward to every day. Not to mention, it's an activity that you can do together with your little one, strengthening your bond.
To make the leash walking experience as safe and comfortable as possible for your cutie, get a harness for her body. The harness will prevent your little one from separating from the leash if she's feeling uncertain or scared about the whole thing at first. It will also allow you to "steer" your kitty around without choking the poor thing. Play it safe and make sure that any harness and leash you purchase is specifically designed for small kittens.
The Humane Society of the United States recommends only walking kittens and cats in low-key areas that don't have a lot of unleashed dogs walking around. The last thing you want is to scare your kitty away from ever using a leash again, so use your finest discretion before walking out the door.