Bigfoot is a legendary creature that the iCarly gang tried to search for in Mount Baker National Forest. It was never seen, however, but it was heard. It attacked Spencer in the woods, while the rest of the gang found out that Dr. Van Gurben had been impersonating Bigfoot. The gang went looking for Bigfoot, only to hear him leaving at the end of the episode after stealing their RV.
In this blog by Carly, she states that Bigfoot was the one who stole the RV, and that he bought an XXL Shiatsu Foot Messager, deluxe nose and ear trimmer, adult diapers, and round trip airline tickets to Nepal.