Complex sentence: Mr. Peanutbutter was the star of "Mr. Peanutbutter's House" which BoJack claimed to have "borrowed the premise" from "Horsin' Around", and has had a stint at filming a celebrity reality show called "Peanutbutter and Jelly".
Split into simpler sentences: Mr. Peanutbutter was the star of "Mr. Peanutbutter's House", which, according to BoJack, "borrowed the premise" from "Horsin' Around". He also had a stint at filming a celebrity reality show called "Peanutbutter and Jelly".