"In a pig's eye!" is indeed an idiomatic expression that basically means "It's NOT going to happen!" at the same time it serves as a challenge to "Try and make it happen!" Again, not perhaps the best pun around, but it was the expression that hit my mind as I was trying to think of a more cerebral joke as opposed to the slapstick of the pratfall with something gooey involved.
"Think your dad will let you go?" "In a pig's eye!"
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Date: 2016-03-20 04:24 am (UTC)"Think your dad will let you go?"
"In a pig's eye!"