Once upon a time I found and played a game where the character goes to investigate a missing spaceship on an alien planet. The planet is covered with a giant organism, which is being experimented on by this crazy scientist guy. The protagonist crashes, and the apparently sentient planet, who calls the scientist guy father, gives the character an alien biological armor to protect him and fight father so that the sentient planet might be freed.
The planet thinks itself stupid, because father told him so. The alien suit has three modes: a human mode, a hulkish form with a big gun, and a smaller dog-like frog with a prehensile tongue which can also climb up walls. The main character has to assure the alien sentient planet isn't dumb and give it some emotional support. Even if the suit is weird.
The crazy scientist guy is using the alien planet to make bio-robots or something. The suit regenerates by tapping into veins. The environment is organic yellows and purples. The suit is mostly yellow with black highlights and tendrils coming off the back.
I believe it was either PlayStation 1 or 2.
You basically went around as a third person shooter, sneaking along walls, fighting enemies, sometimes hiding behind a bio force field the living planet threw up to protect you in safe areas, transforming into the big guy to shoot the giant cannon.