Hahahaha...no I dont think "You need to hit the Frock and speed down the rocket for finding Kloppstock the rock." is the answer....Gerbil is just....Gerbil.
If I remember correctly, Frog Rock is inbetween a tree stump, and a big cloud, itll be the only rock inbetween those two things, and doesnt really look like a frog.
When you see it, you stop on it, and exit the view from the binoculars I believe, and Sam should say something.
You MIGHT have to click on something in the binocular view, but I think you just stop on it, and leave the binoculars to get the commment and continue.
Good luck. I always thought it looked pretty cool when you add all the big foot hair and stuff to the rock.
Edit: You totally shouldnt need a walkthrough.....I uh....well I beat this game before I was 10 i think...