Pufferfish will affect you if you are in creative and give you the effects nausea, hunger and poison.

How to recreate
1: Eat a pufferfish in creative mode

Expected
Pufferfish does not give the creative player any effects

what actually happens
Player will gain the effects nausea, hunger and poison

Note: this may also be an intentional feature, but there is nothing about it that i could find and wither roses aren't supposed to give effects in creative