What is the Nosotros form of gustar?

Gustar is one of those odd verbs that is conjugated not by the person, but rather by the object. Gustar literally means "Is pleasing to"

So when you say "Me gustan los gatos" you are really say "The cats are pleasing to me"

Therefore, in the preterite form you only need two forms or gustar. The 3rd person singular and plural forms which are

gustó -- It was pleasing to...

gustaron -- they were pleasing to...