I've seen something like that, but it could also have been my imagination
No.
No, there's no such thing and lagged Steve are just things people just made up.
Lagged steve? I have never heard, seen or read before. Well, there's never been anything like that in a normal game. There are mods and plugins for this.
It's a steve with long legs i was in a single player world and suddenly there was such a figure on the left of the screen but it can also be a buggy enderman which i don't believe
Can just be an enderman or an imagination.