The Communication Test

Cast (in order of appearance): Calvin Jacobson, Hobbes Jacobson, Susie Derkins, Andy Adams, Socrates, Sherman, MTM

Plot
MTM gets a mysterious message, but who is it from?

Transcript
The Communication Test Transcript

Trivia

 * This episode is probably a reference to a story arc where Calvin gets a letter from an anonymous "spy", but it turns out it was really Hobbes.
 * This is the ninety-second episode of Calvin and Hobbes the Animated Cartoon Adventures.