My game procedurally generates the environment from simple images with low transparency drawn with additive blending. It does this by filling in a pair of lists of visuals to draw (one for foreground and one for background). Each element of these lists contains the position and an indication which entry in the list of sprites to use.
During generation, the tree sprites and their reflections can be flipped, in which case the expression for which sprite gets a possible +1 added to both, using a variable to make sure the reflection matches. Due to having named the variable too similarly, though, I initially added the constant for the position of the reflected tree sprite. Normally, this would result in trying to draw a non-existent sprite, which silently fails. However, because I made and included far more art than the jam build uses, this effect happened:
(also shown in pic: the result of my having both forgotten to manually set the anchor, aka sprite origin, for the oar and forgotten to make sure it's applied in all the right spots. In this build it rotated all the way around the boat from that distance.)