The Mulberry Tree: Shakespeare appears to be very familiar with the mulberry and uses the tree as an image in plays such as Coriolanus and A Midsummer Night’s Dream. One wonders how such an exotic and rare specimen, introduced to England by Queen Elizabeth or James I depending on which story is to be believed, would find its way into the imagery of the rustic bard Shakspere writing in London surrounded by the dirt and grime of city streets. Later, when he retired to Stratford, he is rumoured to have planted a specimen which was later chopped down by a subsequent owner of “ New Place”.
Catholic scholars have noted that Campion had a presentiment of his martyrdom which occurred in the guise of a vision he saw while living at Brunn, wherein the Virgin Mary appeared to him in an old mulberry tree in the monastery garden. 
It is easy to imagine Campion observing the growth habit of the tree in the monastery garden, basking in its shade, eating its fruits and it seems natural that such a familiar object of his everyday life would find itself represented in his creative work.
De Anima: In discussions of Shakespeare’s thought it has been noted that he was influenced by the writings of Aristotle and St. Augustine, especially their treatises on De Anima, the nature of the human soul.  The concept finds its way into such plays as Twelfth Night, Hamlet and Troilus and Cressida. Campion was so interested in this topic he actually wrote a poem on the subject in Latin called De Anima.
An old proverb?: Campion and Shakespeare were the first Englishmen to put down in writing a proverb about taking eggs for money. In The Winter’s Tale Act I Scene ii, Leontes asks Mamillius the question “My honest friend, will you take eggs for money?”. In his History of IrelandCampion has the Earl of Kildare exhorting “He is no more to blame than his brother Ossory, who (not withstanding his high promises) is glad to take eggs for his money” . One wonders whether this proverb was commonly known.
If not, Shakespeare may have appropriated it from Campion’s History or it could have been one of Campion’s idiosyncratic phrases that he made use of in prose and drama.
The 1598 Quarto: This edition of Love’s Labours Lost carries the words “newly corrected and augmented by W. Shakspere.” Is it not strange that this first known book to appear with the dramatist’s name attributes a W. Shakspere with the correction and augmentation of the play not its authorship? Why is his name spelt this way unlike the more familiar Shakespeare which is the spelling used in the printing of the poems?
Perhaps because the poems were printed in their original form and there was no need to draw attention to the fact that they were tampered with by somebody other than the author.
Campion the Poet:
A number of Campion’s contemporaries praised his abilities as a writer and poet in language that evokes the words used by others at the time to describe the nature and achievements of Shakespeare. In the Concertatio Ecclesiae (1583) a Latin sentence proclaims of Campion that “you were the leader of the flock; the rest of the crowd gave first place and the palm to you”. . Sir John Harington remarked, in 1602 that “Campion the daungerous Jesuit spoke eloquentlie in prose and sweetly in verse”.. Sir Phillip Sidney, Robert Persons, Richard Bristow and Thomas Stalpeton commented on his status as the “observed of all observers”. Gerard Kilroy presciently remarks that “we may have some of his poetry and prose without knowing it”. 
The Peacham Document: This document portrays a scene from Titus Andronicus drawn by a Henry Peacham who appears to have been in the audience of a performance of the play. In recent times it has been concluded that the scene depicted is evidence that an earlier version of the play existed and that the drawing on the document was made by Reverend Henry Peacham, not his son. A Latin abbreviation on the document has been interpreted as giving the date of the drawing as 1574 or 1575, thereby making it impossible for William of Stratford to be the original author unless this rustic genius was so brilliant he wrote the play aged ten or eleven. 
Two Earls called Henry: The second Earl of Southhampton was also named Henry Wriothesley. It is possible this second Earl, a Catholic dissident, was the dedicatee of Shakespeare’s early poems not his son. Campion would have known this Henry from St. John’s College at Oxford and sympathized with his plight when he was incarcerated in the tower. He died, strangely enough, in 1581 the year of Campion’s execution.
The Missing Link: Over the years critics have noted that the only character Shakespeare had not attempted to portray was that of the missionary priest . In his recently published imagined biography of Shakespeare, Will in the World, New Historian Stephen Greenblatt follows this trend in finding it noteworthy that among the vast array of human types that Shakespeare drew – prostitutes and sorcerers, pickpockets and Egyptian Queens - the only one of which he never attempted a sympathetic portrait is the saint fanatic, the visionary religious.  Could the reason be that Campion himself was the prototype for the English missionary priest and thus had no precedence to draw upon when peopling his plays? Perhaps this character was too close to home and he didn’t have the necessary objectivity or the desire to peer too closely into his own heart and mind.
Spenser’s Aetion: In his poem Colin Clout Spenser talks of England’s great poets finishing with this stanza:
Critics have wondered whether this penultimate poet described by Spenser was no other than Shakespeare. Derbyites have tried to claim it as a reference to their candidate. If Spenser was indeed alluding to Shakespeare who else but Campion, whose name so closely resembles the word champion, could “like himself heroically sound”?