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.
- Grittings. Ma nam is Kahlfin.
- Hoffa gud tay.
- Grittings. Ma nam is Kahlfin. Heer yor lunboks. Hoffa gud tay askool.
- It troo! Dat darn Kahlfin stole ma spacechip!