Just to let you know, Rocko is actually listed as an INFP on this page.
Eh, I don't believe a lot of the online sites that type people. They could be right, I just didn't analyze it closely. Okay...
I/E - No question he's introverted. Even if you watch one episode, you can immediately tell. Definitely I.
S/N - He tends to have a little bit of imagination and he does tend to fantasize a little, but I'm really thinking he's more of a sensor type because of his practical nature. He's quite pragmatic, and he doesn't really live in the future.
T/F - This is also difficult. I'm leaning toward F though, he seems like he's not a very confrontational guy, and he is sympathetic, so F.
J/P - I feel he's P. He's not really scheduled or structured. He does things to the last minute, and often misses the bus (in the figurative state).
Looking at the cognitive functions, he's more INFP than ISFP. So yeah, he's INFP. That makes sense now as far as his personality goes. He's definitely a Type 6 enneagram.