I made pet fierballs and they do little lag.
They bounce and follow you around, can sit, attack people, and defend you. Along with some other trivial commands.
Bots really don't lag that much, it just depends on how many calculations and such you are doing as well as how many bots there are. If you're just moving the bot to an already determined point(i.e location of last thrown stick) then it wouldn't be that laggy until you started adding more and more bots, and more complex commands.