“Ooops, I sued the wrong person. My bad.” In this Rule 21 original proceeding, plaintiff, the estate of a worker killed on defendant’s property, sued defendant just within the 2 year statute of limitations period. After it passed, it turned out that another party was the proper defendant. Plaintiff moved to amend to include the correct defendant under CRCP 15(c), claiming the amended complaint related back to the timely-filed original complaint. The trial court dismissed because the new defendant was added 116 days after the filing of the original complaint and after the statute of limitations period had run. The Court reversed and held that amending a complaint and serving a new defendant within the time for regular service under CRCP 4(m), 120 days, was a reasonable amount of time. On remand, the trial court must determine if the delay in notice was otherwise unreasonable.