In Episode 348, Zack explains that the keyboard is sticky because he accidentally dumped a church collection bucket of other people's jizz on it.
In Episode 371, Zack's character went to the right many times. He claims that he was "sleepy", but we all know he was fapping, and that the jizz did the work.
The sticky keyboard strikes again in Episode 372 about 16 minutes in when Zack is making a shitty house.
In Episode 438 the jizzed soaked keyboard strikes again when Batman starts running into a wall.