What I expected to happen was...:

Suffocate

What actually happened was...:
Entered a block

Steps to Reproduce:
1. Set up like the picture below. Regular piston on bottom, and sticky piston on top.
2. Pull the piston, and you'll suffocate like the picture below.
3. Break the block on your view. Also, you won't need blocks surrounding you if you're doing it with glowstone, and mobs won't need any support blocks, even if it's in a diamond block. It won't get pushed out.