^{Update by Mega_Spud}

The speed effect doesn't apply to all mobs/entities.

What I expected to happen:
I expected the command /effect @e speed 150 50 to apply to all entity/mobs

What actually happened:
Several mobs were unaffected.

Steps to Reproduce:

• Use the command /effect @e speed 150 50
• Notice that some mobs are not affected

List of mobs that don't appear to get the speed affect (update):

• Creeper
• Villager
• Zombie
• Pigman
• Sheep

Original Description:
Steps to Reproduce

1.Use the / effect (Speed) command on some mob for eg a zombie. As you can see the zombie still gets its normal speed instead of increasing it