I am really sorry to hear that your fellow Teddy ate clumping cat litter and cat feces.
The quantity that he ate is the most important part. Though clumping litter is more likely to create a sand effect on the gastrointestinal system it can lead to an impaction and irritation, and the quantity that he ate can determine whether an impaction occurs.
If he ate a large quantity of litter within the last 2 to 3 hours it is worth trying to get him to vomit at least some of it back up.
You can give him 1 tablespoon of 3% hydrogen peroxide per 10 pounds of body weight soaked up with bread chunks or a small amount of dog food or ice cream (no more than 4 tablespoons even if he weighs more than 40 pounds).
Then take him outside and run him around to get the peroxide bubbling so he vomits.
If no vomiting in 10 minutes repeat the peroxide dose once.
If he vomits any of the litter that will help.
Once it has been longer than 3 to 4 hours it may be too late, and the litter is likely out of his stomach.
If you cannot get him to vomit I recommend feeding with a vaseline sandwich. Take a slice of whole wheat bread, slather with vaseline (or any generic petroleum jelly) as you would peanut butter on a slice of bread, cover with a second slice. Feed it to him bite sized piece by piece or he will make a huge vaseline mess. This adds fiber and hopefully makes the litter slide rather than compact.
Whether you get him to vomit or not feed a homemade diet of 1/3 boiled, lean hamburger or boiled, white, skinless chicken, all fats and juices drained off the meat, and 2/3 white rice. Add 3 tablespoons of canned pumpkin, not pie filling just pumpkin, to each meal for fiber to help push the litter through and cushion the irritant effects of sand on the gastrointestinal tract lining.
Signs that things aren't going well, and he needs an immediate veterinary visit, are vomiting, a tense painful belly, lack of an appetite, a fever (more than 103.5F rectally) and lethargy.
If it doubt at all that things aren't going well it is always best to have him checked.
If things go well and you believe the litter has been pushed though, and he continues to feel well then start mixing in his regular food, adding a little more regular and less bland at each meal. It should take a week to get him converted back to his regular food.
Let me know if you have any questions.