What did Severus want to do as an alternative career? He actually declared his secret passion to Draco after dragging the young student into the bathroom.

(Notice how I avoided the pron there.)
The Potions Master wanted to be a Master Thespian! Here is a version of the later bathroom scene in HPB between Draco and Snape (where I obviously copied the figures - or tried to). They were both ACTING! Genius!
Of course, Snape's greatest bit of ACTING! took place in the Shrieking Shack in DH. ;-)
ArtPad for fussiness over skill.
No! It is I who fooled you! For I am dead.. and merely acting alive!
Genius!
But... he fooled us again! He was really alive... and merely acting like a dead man acting alive! Bwaha!
Truth to tell, though, by the time DH was done, we really didn't know how much of it was ACTING!