When the four Athenian lovers are discovered asleep on the edge of the forest and then woken up by Theseus and his hunting party, it is Lysander who first responds to the inevitable questions about why they are there all together and what happened to them. Note how he replies to his Duke's question:

My lord, I shall reply amazedly,
Half sleep, half waking; but as yet, I swear,
I cannot truly say how I came here.
But, as I think--for truly would I speak,
And now I do bethink me, so it is--
I came with Hermia hither. Our intent
Was to be gone from Athens, where we might,
Without the peril of the Athenian law--

Note the way that Lysander gives rise to the "dream" of the title of the play as he tries to recall what has happened to both him and to them all during their night in the forest. His response is very vague as he struggles to remember what seems to be nothing more than a dream or a fantasy, and he is only able to remember, after thinking about it, the definite reason that led him to the forest in the first place. He is thus startled, confused and distracted.