I have two stock responses. If someone tells me something, no matter the importance level, I say "marvellous", nabbed from Red Dwarf, or if something goes wrong, I use the phrase an old school friend of mine used a lot, "Life's a b***h and then you die"
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"Think like the whelp, think like the whelp, think like the whelp... " Captain Jack Sparrow
"Hello. My name is Inigo Montoya. You killed my father. Prepare to die." Inigo Montoya