Short answers, pulled from the story.
Scholars suggest that Thomas Kyd wrote approximately 60% of Edward III while William Shakespeare contributed about 40%. Brian Vickers used computer analysis in 2009 to detect these plagiarism patterns within the text. The play emerged from a team effort early in his career.
Pages within the manuscript of Sir Thomas More contain handwriting believed to be Shakespeare's own. The assembled text represents a collaboration primarily led by Anthony Munday alongside other contributors. These physical traces offer rare tangible evidence connecting Shakespeare directly to collaborative revision processes beyond printed plays.
George Wilkins wrote the first two acts of Pericles Prince of Tyre according to most scholars. William Shakespeare is credited with composing the final three acts of the play. Later research by MacDonald P. Jackson appeared in 2003 reinforcing this division of labor between the two writers.
Thomas Middleton may have adapted Macbeth by introducing Act Three Scene Five featuring Hecate and three witches alongside a song also found in his work The Witch. Timon of Athens might result from collaboration between William Shakespeare and Thomas Middleton explaining its incoherent plot and unusually cynical tone. Emma Smith and Laurie Maguire published research in 2012 suggesting dual authorship for All's Well That Ends Well at Oxford University.
Henry VIII is generally considered a joint effort between William Shakespeare and John Fletcher. The Two Noble Kinsmen appeared in quarto form during 1634 with both names listed on the title page. Each playwright appears to have written roughly half of the text despite exclusion from the First Folio.