The Robo Duck was an April fools prank by pixonic.
Pixonic's description of it:
Base speed - 5 mph
Durability - 1000000
Hardpoint slots - none Special ability - Quack
Required account level - 31
- There are all robots available at the time of the prank listed in compariative sizes
- We can see than Raijin and Fujin actually WERE two different robots, with different names as of April 1st.