Every Furby is born speaking only Furbish, then slowly learns English as you love on it. Here's the dictionary straight from the 1998 manual (via the Official Furby Wiki, CC-BY-SA) so you can translate what your weird little friend is shouting at 3am.
Doo? — Hi / Hello
Doo-doo — How are you? / Baby
Wee-tah-kah-loo-loo — Tell me a story
Wee-tah-kah-wee-loo — Go to sleep
Eh-oh — Oh!
Oo-tah — Eat
Ah-ay — Yes
Noo-loo — No
Bo — Bored
Dee-oo — Duty / Need to poop
Oo-boo — Scared
Kah — Cat
May-may — Mommy
Pa-pa — Daddy
Bay-bee — Baby
Dah — Dance
Nuk-nuk — Nuzzle
Sing? — Sing?
Way-loh-moo — What's that?
Koh-koh — Hold me
Want the full manual? Grab the free text copy on the Sick Furby page, or see my Care & Repair Guide.