Board Thread:Naruto Discussions/@comment-25374031-20140917212238/@comment-25431556-20140917220212

Jiraya Sage Mode is not complete, he needs Fukasaku and Shima to be with him in order to control the nature chakra. The frog appearance means the user inst completly controlling that power, if he continues would be transformed into stone (this is why those 2 frogs stand on his shoulder). Naruto on the other hand, due its large chakra reserves, can master sage mode, and not showing any physical traits of frogs (except the eyes, and the yellow things arround it, these are the marks of a true sage).