"We like the fat peacocks."
Translation:Pavones pingues nobis placent.
IMO, Duolingo doesn't handle this sentence very well.
"nobis" is an example of the dative case, which is most often used with indirect objects (like "He gives a book to us" -- in Latin "Librum nobis dat"). In this sentence, the verb "placere" (literally "to please") takes a dative object instead of the accusative that you might expect. Duolingo really doesn't cover the dative case at all, except in a few sentences like this one.
You can think of the Latin grammar as roughly parallel to the English "Fat penguins are pleasing to us", except that the Latin sentence is definitely not as passive as that, and "We like fat penguins" is a much more natural translation into English.