Four aliens — Dopey, Sleepy, Happy, and Moody — from the planet of liars and truth-tellers are having a conversation.
Dopey says to Sleepy: “You are a liar.”
Happy says to Sleepy: “You are a liar.”
Moody says to Happy: “They are both liars.” Then, after thinking for a moment, Moody adds a final statement: “You are also a liar”
Which of the four aliens are telling the truth?