How many characters double cast in a midsummer night's dream?

Answer 1

Egeus, Philostrate, various Fairies including Mustardseed, Cobweb, Peaseblossom and Moth, who has only two words to say: "And I."

Answer 2

It really depends on how big a company your have to play the play. Some scholars believe that there were only thirteen actors in the Lord Chamberlain's Men at the time this play was written, unless they hired extras. Since there are 21 speaking parts in the play (although Moth is perhaps the smallest speaking part in all of Shakespeare), that would mean that practically the entire cast would be doubling some other part. Possibly Will Kempe, who played the part of Bottom, may have been too recognizable to have doubled any part.

For the last act, it is clearly necessary to have actors playing Theseus, Hippolyta, Hermia, Helena, Lysander, Demetrius, Bottom, Flute, Snug, Starveling, Snout and Quince all on the stage at the same time. That's twelve. Philostrate is present at the beginning of the act, but is not heard from once the play starts. At the end of the play, Puck comes on and has an apparently pointless speech starting "Now the hungry lion roars". This speech is obviously given to give the rest of the cast a chance to change costume and to reappear as the fairies.

Even when it is not necessary to do so, productions not infrequently double Theseus with Oberon and Hippolyta with Titania, with Philostrate doubling Puck. This was done in Adrian Noble's well-known umbrella and hanging light bulb production.

It is easy to see how Egeus could have doubled one of the "mechanicals" and the parts of the fairies like Moth and Mustardseed taken by the young lovers, if you had a particularly small cast.