Kahlfin was the name used by a mysterious shapeshifting alien who transformed into Calvin's shape just before Susie Derkins arrived at the bus stop, and is also used to refer to Calvin later in the comic. He spoke little English; copying what Calvin said, but poorly. "Kahlfin" is an obvious mispronunciation of the name Calvin. Before changing shape, he spoke in an alien language consisting of simple shapes and lines. He later learned other English vocabulary, as seen by his last line.
- Grittings. Ma nam is Kahlfin. (Greetings. My name is Calvin.)
- Hoffa gud tay. (Have a good day.)
- Lunboks. (Lunchbox.)
- Grittings. Ma nam is Kahlfin. Heer yor lunboks. Hoffa gud tay askool. (Greetings. My name is Calvin. Here's your lunchbox. Have a good day at school.)
- It troo! Dat darn Kahlfin stole ma spacechip! (It's true! That darn Calvin stole my spaceship!)