Doggy Downers, etc.
Valium (diazepam) works well. If you have a friendly veterinarian, tell him what you're doing and maybe he'll write a prescription. If somebody in the family already has some, 2-1/2 to 5mg should calm a cat or a small dog down for a while, although I did have to give a seriously agitated cat a good bit more than that one time.
Start with a lower dose because some critters (like humans) are more sensitive to it than others. Mix it with a little food right before you give it, otherwise they might spit it out. If somebody starts getting too agitated before you get where you're going, give them about half of what you gave them before, just to get their blood level back up.
It tends to be an appetite stimulant in cats (cat munchies?), and can cause them liver problems if used more than occasionally. Sometimes you'll run across a critter that starts acting crazy when under the influence. Again, kinda like humans.