Tell it to the marines!

(go) tell it/that to the marines

A scornful or incredulous response to a story or statement that one does not believe or finds ridiculous. A: "You know, my dad used to play basketball with the president when they were both kids." B: "Ah, go tell it to the marines! Why do you tell such fibs?" A: "I bet you I could eat 20 hot dogs in less than half an hour!" B: "Tell that to the marines, pal!"
See also: marine, tell, that
Farlex Dictionary of Idioms.

Tell it to the marines!

Inf. I do not believe you (maybe the marines will)! Your excuse is preposterous. Tell it to the marines. I don't care how good you think your reason is. Tell it to the marines!
See also: tell
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • (go) tell it/that to the marines
  • marine
  • tell it to the Marines
  • tell it/that to the marines
  • tell that to the marines
  • (Go) tell it/that to Sweeney!
  • cockamamie
  • Don’t make me laugh!
  • don't make me laugh
  • Don't make me laugh!