"Draw a pony up to no good / Draw a pony with twisted thoughts."
Bit of experimenting there. It helps that Sprout's got those eyebrows which… stand out, compared to the others'.
I'm pretty sure I've done this joke before. It probably tells you something when my brain immediately leaps to this when someone is up to no good, lol. Might just make it a tradition to draw a pineapple at least once each year.