Rip-off or not, it was actually good and worth watching compared to a lot of shitty Animes out there. Last season didn't live up to it's hype but it was forgivable since it's Nickelodeon.
I'm most surprised that they didn't drag on the series for decades like most Nick series. In a way, I'm the they ended it before they had chance to ruin it to no return.
And oh yah! I hate those dam duck-turtles, salamander-eel, duck-beer, chicken-horse(I know this is from another anime). Those animals were funny but really annoyed the hell out of me. it was so unoriginal, just toss 2 animals and bam. However most people such as I loved Oppa the flying bison and the giant badger moles were acceptable.
In a way all anime is a rip off of another anime, one way or another. But this still had originality and flare to it, even if it acquired some of its elements from other sources. Just like martial arts.