From the ArcaMax Publishing, Jokes Newsletter:
http://www.arcamax.com/news/jokes/s-368096-328567
A doctor, an engineer, and a fungal taxonomist arrived at The Pearly
Gates.
The doctor said how he'd healed the sick, helped the lame; but he was
a sinner and was sent to Hell.
The engineer told how he'd built homes for the homeless, etc.; but he
messed up the environment, so he was sent to Hell.
The fungal taxonomist was frightened by all this, but as soon as he
mentioned his occupation, God said "You've already been thru Hell,
Welcome to Heaven."