Has an airplane ever been launched from a submarine?
Yes, 

The HMS M2 had a single seaplane aboard that it was capable of launching. 




  Her 12-inch gun was removed, replaced by a small aircraft hangar, the
  work being completed in 1927. This could carry a small Parnall Peto
  seaplane, specially designed for the M2, which, once its wings had
  been unfolded, could be lowered onto the sea alongside by a derrick
  for take off. On landing, the aircraft was hoisted back onto the deck
  and replaced into the hangar.


...


  In October 1928, a hydraulic aircraft catapult was fitted, to enable the seaplane to take off directly from the deck.


The I-400 class submarine was also capable of aircraft launches.


  The type name was shortened to Toku-gata Sensuikan (特型潜水艦 Special Type
  Submarine). They were submarine aircraft carriers able to carry three
  Aichi M6A Seiran aircraft underwater to their destinations. They were
  designed to surface, launch their planes, then quickly dive again
  before they were discovered.


There are some more info blurbs here worth checking out about various submarine/aircraft creations.