Tennis balls are significant in which Shakespearean play?

Question: Tennis balls are significant in which Shakespearean play?

Answer: In Act 1, Scene 2 of Henry V, the King of France sends a "gift" of tennis balls to belittle England's beloved King Henry:

First Ambassador Thus, then, in few. (250)
Your highness, lately sending into France,
Did claim some certain dukedoms, in the right
Of your great predecessor, King Edward the Third.
In answer of which claim, the prince our master
Says that you savour too much of your youth,
And bids you be advised there's nought in France
That can be with a nimble galliard won;
You cannot revel into dukedoms there.
He therefore sends you, meeter for your spirit,
This tun of treasure; and, in lieu of this, (260)
Desires you let the dukedoms that you claim
Hear no more of you. This the Dauphin speaks.
KING HENRY V What treasure, uncle?
EXETER Tennis-balls, my liege.
KING HENRY V We are glad the Dauphin is so pleasant with us; (265)
His present and your pains we thank you for:
When we have march'd our rackets to these balls,
We will, in France, by God's grace, play a set
Shall strike his father's crown into the hazard.
Tell him he hath made a match with such a wrangler
That all the courts of France will be disturb'd
With chaces.

The author from whom Shakespeare received most of his historical information, Raphael Holinshed, explains it best: "they presented to him a token [tennis balls] that was taken in verie ill part, as sent in scorne, to signifie, that it was more meet for the king to passe the time with such childish exercise, than to attempt any worthie exploit." (Chronicles). That the game of tennis, so popular in England, was a French invention would have been a further insult.