Who said this phrase first?
Noah while loading the animals. 
As for when it was first said on TV, I’ll guess it was on a program called You Asked For It!
Well, the first place I ever heard the phrase was on Channel 11 in New York during the 3 Stooges Hour with Officer Joe Bolton.
The Stooges became hugely popular again during the early 1960’s, in part because of TV shows like Officer Joe Bolton’s. And naturally, little boys like me and my friends would imitate all their slapstick routines- including poking each other in the eye, pulling each other’s hair, twisting each other’s noses, slapping each other, etc.
Officer Joe was constantlky telling kids “don’t try this at home. The Stooges are TRAINED PROFESSIONALS.” A few times, he even brought the elderly Moe Howard into the syudio to tell us kids that we should never do what we saw the Stooges doing on TV.
I think Daffy Duck said it in the cartoon where he ingests all the flammable material and blows himself up.
Bugs says something like, “Great trick, Daffy.” Daffy replies, “Yeah, but I can only do it once.” (Obviously after the other quote.)