I've tried a few addons in the past, but all of them seem a bit too fancy for me. I just want a random pet out with one click; not interested in the bells and whistles.
So I'm sticking with my trusty macro:/run CallCompanion("CRITTER", random(GetNumCompanions("CRITTER")))
There's probably a newer and simpler version of the macro for summoning a random companion these days, but I've stuck with this one since forever and it hasn't failed me yet! XD