You, Carl, and Ron all got in trouble for teaching the kids stuff that they shouldn't know.

So, you all got sent to a cell, the same one, and had to stay there for a night as punishment.

Out of boredom, you put colorful lipsticks on them. Blue for carl, red for ron.

When you finally got let out, Rick noticed kiss marks on your neck, on red and blue, and your lips were colored a deep purple.

He also noticed the red on Ron's lips, and blue on Carl's lips, and put two and two together.