I believe this works with any cable provider if you want to get Showtime. Call your service provider and order Showtime, then follow the steps below.
From the website:
A $25 Rebate Offer from Showtime is available to new Showtime subscribers only. To receive your $25 Rebate from Showtime, print your name, address and phone number on a 3×5 card and mail the card along with three months of original cable bills indicating your SHOWTIME subscription and dated between 2/1/07 and 3/31/08, to: SHOWTIME Rebate Offer, P.O. Box 1222, Department TBA, Grand Rapids, MN 55745-1222. Your response must be postmarked by 4/14/08 and received by 4/28/08. This offer expires on 12/31/07. This offer cannot be combined with any other SHOWTIME promotional offer and there is a limit of one SHOWTIME promotional offer per household in any 12-month period. Your $25 Rebate from Showtime will be mailed to you within 8-10 weeks after the receipt of your valid submission of the aforementioned documents. Please keep a copy of all documents for your files. This offer is executed and administered solely by SHOWTIME NETWORKS INC. and the offer is good while supplies last.
I guess you can order Showtime, watch your favorite shows, get your $25 bonus, and then cancel it.