My first guess is that the crocodile would eat the frog, so he wouldn't lie about it since he'd be happy as well. So my take on the metaphor then is take good news on an obstacle being overcome or some evil being rid of exactly how it was delivered as long as the messenger would be happy about it as well, if that last part makes sense.
It's probably not true at all, because I'd have obviously partaken in a serious dosage of psychedelics. Either way I'd take the opportunity to make sure it's dead for myself. Possibly putting a bullet hole through my apartment floor in the process.