not allowed on dining plan (no appetizers on regular dining plan at all) If you're on deluxe dining, many places have appetizer-for-two choices that can be ordered using credit from each person.
But, if you're paying cash, an appetizers-only meal is a great way to get a variety of great foods to share without breaking the bank. Almost like eating at a tapas restaurant. We've been on the deluxe dining plan many times and we're often lamenting how large the appetizers are at most Disney restaurants, with a few exceptions...so many seem to be huge for one person. Just this weekend we ran into that at Whispering Canyon and Kona Cafe...the appetizers were over-large portions. Even at Kona the sticky-wings for two was very large. WE both thought we could have made an entire meal out of the sticky-wings for two, the fabulous Kona bread, a small salad to split and a dessert to split. And we would have walked away full, too.
The only places we find some smaller appetizers not big enough to split would be at Coral Reef; also most of the signature restaurants have small appetizers (seems like the signature apps are more about exotic items/flavors and extremely decorative presentations instead of quantity.)