I saw an early (think mid-90's) attempt at this when I was in college. The only tripod that was successful was something along the lines of what kangaroos do, hopping with two while using a robust tail as a spring.

Most quadroped mammals can run by moving their legs in pairs, in this mode one of the pairs could be replaced by a single leg. Would make normal walking awkward though.

And indeed some almost exclusively move like that, namely leporids (rabbits and hares). They do not have a regular walking gait because the back legs are so long and specialized for jumping.

Have you never played Spore? :)

It was pretty good at this. Great fun for experimenting with locomotion.

Evolutionary pressure was never baked into the final game - it was all intelligent design. This was a missed opportunity, in my opinion.

Spore share a surprisingly similar trajectory to No Man's Sky. Overpromised, underdelivered. Hey, I guess that's just like AI!

That's true, but it did figure out the locomotion for you no matter what way you designed it. I ran into very few creatures that couldn't move.

It's pretty primitive if you go back and play it, but the locomotion system is something I haven't seen in any other game.

Quadroped animals with a missing (or bad) leg move quite effectively.