I used to watch this cartoon when I was little, maybe around 2007, although I think it was older than that. I am not sure, but I think it was an anime. I do not remember it clearly but there was a boy and a girl who fought the bad guys. The boy and girl used to travel with the help of a giant robot or machine, they hopped on the legs of it. I think the robot looked like a cat (?) or some other animal. I've been searching on Google, but I can't find it with the little info I remember.
Of course the two heroes had different robots, that were dogs, elephants, pelicans, pandas (I don't remember any cats), but the basic description corresponds: a boy and a girl who travel on the legs of a robot.
In that series, usually the bad guys were the true protagonists (and were usually very funny); they usually fought using small robots that came out from the mouth of the main robot
I'm distinctly getting a Sym Bionic Titan feel from this question. Posting a visual for the OP to reference:
I came to this conclusion from these details:
.....around 2007, although I think it was older than that. I am not sure, but I think it was an anime.
This series focuses on a trio made up of "the alien princess Ilana, the strict, but rebellious soldier Lance, and the robot Octus; the three are able to combine to create the titular Sym-Bionic Titan." The titan could be seen as the robot, and though the years are a bit off the animation [not the art itself] used by creator Gennedy Tartakovsky was anime-inspired [as seen by the big eyes and hair], but not anime itself.