For April Fool's Day, Heckle & Jeckle are "A Couple of Songbirds Today", as the song goes, in "Taming The Cat", from 1948.
A canary has fallen victim to a nasty housecat, who then puts up a "Songbirds Wanted" sign, attracting Heckle & Jeckle. One plays the piano, while the other mimics Jimmy Durante in performing "A Couple of Songbirds Today". Ned Sparks speaks for both Heckle & Jeckle, and also does the singing, one must assume.
Uploaded by Pat Hawkins to YouTube:
It's a shame the boys are locked in Viacom's vaults now. You'd think Nickelodeon would bring them back, but noooooo. The magpies would make today's celebration of stupidity (i.e. Fairly Oddparents) look weaker than it is.