The Tip of the Zoidberg
Futurama Season 8 Episode 10 (08/18/11)
Zoidberg and the Professor meet at Momco and are given the task of killing a Yeti. Zoidberg thinks the Professor is infected with a dormant incurable disease and on top of that is scratched by a Yeti.
Back in the present the diseases symptoms begin to manifest and the Professor asks Zoidberg to fulfill his promises of killing him before it gets too bad. Zoidberg realizes that the Professor has Yeti-ism and is able to cure him.