Timothy
Timothy is the problem of this whole escapade. He caught pneumonia* before moving day. If they moved, he would die. If they didn't move, he would die with everybody else because they would get mowed over by a plow. Timothy is the second youngest in the Frisby family. (Or Brisby, if you want to watch the movie. Spoiler alert: the movie is not as good as the book and if you ask me, the movie is HORR-IB-LE.) Awkward fact about Timothy he was bitten by a spider but lived.
*for more information on pnumonia go to: http://www.webmd.com/lung/tc/pneumonia-topic-overview
*for more information on pnumonia go to: http://www.webmd.com/lung/tc/pneumonia-topic-overview