You see this occassionally in comedy films and I have to wonder how legal it is. If I act as my own lawyer at a trial, can I call myself to the stand as a witness? Can I refuse to answer my own questions and be a hostile witness to myself? Am I supposed to ask a question, then run and sit on the stand and answer, then dash back in front to ask my next question? Can the opposing counsel accuse me of "leading the witness" or "badgering the witness" or whatever?
The old saying: Being your own lawyer means you have a fool as the lawyer and a fool as the client. If one fool calls the other fool as a witness, that's even more foolish. And the worst crime is annoying the judge with your antics.
Opposing council will just take note of every question you ask and your replies, and then call you as witness themself. And assuming they are a proper lawyer, everything they ask will be hurting you. No need to accuse you as "leading" or "badgering" the witness.
Yes, though there is a procedure for in that doesn't involve running back and forth (don't do this as the bailiff will tackle you).
The defendant will almost always need to take the stand. There are two ways this can be done. Which is permitted depends on the judge.
The first, more common method is that the defendant gives a statement without being questioned. This would include all relevant facts that would normally be given by answers to their lawyer's questions.
After this statement is given, the prosecution will cross-examine as usual.
The second is more similar to what you describe- the defendant plays the role of asker and answerer. The defendant does not run back and forth and should probably refrain from doing a silly voice for the lawyer part but yes, they ask questions and answer them. This was used in United States v. Nivica, 887 F.2d 1110 (1st Cir. 1989).