Bottom's role in the play is to be over the top ridiculous to Puck's more sly humor. Bottom thinks he's the best actor in the world even though it's obvious he's terrible and it is only fitting he is transformed into a creature with an ass's head for Titania to attempt to woo.
In the end, Bottom's play that he directs and performs for the other characters serves as a sort of satirical play within a play where his play is an abridged silly version of the actual play (A Midsummer Night's Dream). Bottom ends the characters' roles in the play by asking if Theseus wants an epilogue or a dance and Theseus asks for the dance. The play concludes after the dance with the characters going to bed.