Related Clues:

• Clown(ish)
• Railway engine - mad!
• Mad - train
• Comically idiotic
• Madcap, like a clown
• Barmy (Spanish) — engine (abbr)
• Bats or bonkers
• Off one's rocker, and a hint to what the four longest puzzle answers have in common
• Not just any last character up front is peculiarly funny
• Crazy to Carlos
• In ... parentis, in place of parents
• Crazy in Spain
• Prefix for motion
• Crazy, in Cancun
• Cuckoo in the head