The first line of “The Duck and the Kangaroo” instantly establishes the dialogue form that will continue throughout the poem, with the narratorial voice announcing who is speaking before handing the rest of the stanza over to the Duck’s own words.
These opening lines launch the reader into the story in medias res—that is, right in the middle of the action. The characters receive no introduction, but Lear’s use of the definite article and proper nouns (“the” Duck and “the” Kangaroo) suggests that these will be the only representatives of their species present in the poem. The world is sculpted on a small scale in these opening lines—just two creatures in conversation with each other—even as the Duck longs to see the world expand.
In these first lines, the Duck describes the Kangaroo’s perpetual motion. The use of caesura (the exclamation point in line 2) to break up the Duck’s first line emphasizes the Duck’s awe but also underscores the Duck’s central problem: unlike the Kangaroo, free to hop as it will, the duck constantly faces physical limitations that slow it down, represented, in this case, by the punctuation that immediately pauses the duck in its tracks. Meanwhile, the alliterative “Good gracious! How you hop!” creates a bouncing sensation (especially when read aloud), sonically depicting the Kangaroo’s action. These opening lines also set up the rhyme scheme that will continue for the rest of the poem (each stanza beginning with an ABAB rhyming pattern, in which alternating lines exhibit full, perfect rhymes).
This clear rhyme scheme contributes to the poem's feeling rather like a nursery rhyme. This feeling is echoed by the meter—which is mostly, though not strictly, anapestic trimeter with some iambs tossed in throughout. Substitutions occur even in these first four lines of the poem:
Said the Duck | to the Kang- | aroo,
‘Good gra- | cious how | you hop!
Over the | fields and | the wa- | ter too,
As if | you ne- | ver would stop!
Note how the final foot of line 1 is actually an iamb ("aroo"), as are all the feet of line 2; this da-DUM rhythm comes into play at the same time that the Kangaroo is mentioned, and seems to reflect the hopping of the Kangaroo. Meanwhile, a dactyl opens line 3, with the initial, bold stress of "over" again subtly reflecting the content of the line: the Kangaroo boldly bounces over everything in its path, including the meter! This continues with the trochee of "fields and" before falling back into iambs (the water too, / As if you ne-") and finally finishing with the expected anapest ("-ver would stop!").
Finally, note how line 3 also has an extra foot, making it a line of tetrameter. Again, this reflects the freedom of movement of the Kangaroo—whose hopping expands its world beyond that of the Duck's little pond, just as the meter of this line expands past the expected number of syllables.