Nathan Fillion Nathan Fillion

The Castle wedding is (hopefully) drawing nigh, which means one thing: The battle to be the best man is on!

As you can see in the exclusive first look at Monday's episode (10/9c, ABC) below, Beckett (Stana Katic) has already chosen Lanie (Tamala Jones) to be her maid of honor. However, when Ryan (Seamus Dever) and Esposito (Jon Huertas) learn that Castle (Nathan Fillion) has yet to select a best man, you can see their competitive wheels start turning.

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