たまたま皆んな同じメニューを頼んだって英語でなんて言うの？

A coincidence is an occurrence of events or circumstances that happen without any apparent connection to each other.

The same thing means you ordered the same dish. If you are at a restaurant you can say thing, dish, or item. Without planning it means by chance, by coincidence.

Sheer coincidence = a total coincidence Utter coincidence = a total coincidence 'Sheer' 'utter' and 'total' are all adjectives frequently linked with the word, 'coincidence'.

>Coincidentally we ordered the same thing. Coincidentally means that it was not planned and it just happened to happen that everyone ordered the same thing.

Sometimes, when people go to a restaurant, they may all order the same thing without discussing it before. We could use some good expressions for this situation: "We all ordered the same thing by coincidence!" This could be a more formal way of saying this if this happens at a business meeting or we are mentioning it to the waiter. "We all think alike!" This is a little more of an informal expression. We could say this in a joking way to our friends. It implies that as close friends, we all think in the same kind of way. And that is why we ordered the same meal.

This is a way to note the coincidence that you all ordered the same thing and open it up for conversation. It also puts the fact that you all ordered the same thing into a positive light. I hope that this helps :)