Well, if Ivysaur returned, there'd be two four legged fighters in SSB4....

Also, I'm pretty sure Wii Fit Trainer and Duck Hunt are deliberate decisions. I mean, when you've got as many character requests as Sakurai, you may wanna have some fun and pick characters that NOBODY seriously suggested. Hence why he's the ultimate troll. =P

Well, if Ivysaur returned, there'd be two four legged fighters in SSB4....

 

Also, I'm pretty sure Wii Fit Trainer and Duck Hunt are deliberate decisions. I mean, when you've got as many character requests as Sakurai, you may wanna have some fun and pick characters that NOBODY seriously suggested. Hence why he's the ultimate troll. =P

Well, there's also the fact that fighters like Wii Fit Trainer and Duck Hunt, while seemingly out of nowhere, represent significant parts of Nintendo's history. Wii Fit is a VERY successful franchise so while not many people wanted a representative, it still makes some sense to have one. And Duck Hunt, like R.O.B. and Mr. Game & Watch (and to a certain extent, Pac-Man) is a "retro" character who basically represents a specific point in Nintendo's history and the overall history of video games.

Add in the fact that Sakurai cares more about fighters who bring something unique to the table in terms of their play style and behavior, and there are a lot of benefits to characters like this besides just "trolling".