Servbots are little "lego-men" created by Tron Bonne, first appearing in Mega Man Legends. They serve a big role in Super Smash Bros. Battle Royale, despite not being a character. It cheats into being the biggest assist role in The Battle Arena.
Serving Tron Bonne during Gameplay
As An Assist
As an assist, Servbot has quite a few options. His height makes for some very funny "I thought I hit him!" moments.
Anti-Air: Servbot calls for another Servbot, who comes flying in with a propellor to keep him in the air. This is a lot like his move from Marvel vs. Capcom 2, which actually makes for a pretty good move. Works best to keep your opponent away, but it's surpisingly hard to hit with.
Grab: Servbot gets afraid (of something) and jumps on the opponent's head. He then jumps off of their head, causing them to fall. Works well if your character can combo with an OTG move. Otherwise avoid this move and the pathetic damage that follows.
Projectile: Servbot calls for another Servbot, who comes running onto the field. He throws another Servbot onto the opponent. If you can get this to land, it resets combo's. However it's so hard to hit with it; your opponent can jump out of the way easily. Still, being able to reset combo's is nice. It's okay.
Powerful Attack: It's King Servbot. Like with Tron's Battle Attack, you can manually direct him and use the hammer to damage opponents. This is actually much better than Tron's King Servbot. You can actually combo into and out of this one (after 10 hits your opponent leaves range), making it much more useful. Projectiles get eaten by the King, as well.
Servbot Works Well With...
Servbot is the type of assist that can go with just about everyone; however his uses vary. Most likely you'll only be getting one use out of him per character. His Anti-Air assist works well with The Air Gods, while his Grab Assist works best with those who can hit OTG. His Projectile is extremely helpful for combo-happy characters, like Zero, and big damage dealers, like Bowser.
And of course, King Servbot goes REALLY well with those who lack a reliable approach, like Bowser, Ganondorf, and Ridley.
Servbot Works Badly With...
Servbot doesn't work well with the balanced characters. Although he works well with Tron Bonne, anyone who has a decent air game, approach, and combo setups really have no need for Servbot. Sadly, that's a lot of people.