"20/20" 8 p.m. ABC — The history of the English castle that inspired the series "Downton Abbey." 

"The Millionaire Matchmaker" 8 p.m. Bravo — Patti tries to forge a love connection for fashionista and reality star Courtney Karr ("Courtney Loves Dallas") in a blatant cross-promotional play.

"Ground Floor" 9 p.m. TBS — Brody's overly competitive ex-girlfriend arrives, drawing concern from Jenny.

"My Big Fat Gypsy Wedding" 9 p.m. TLC — Irish ceremonines, including outrageous weddings, over-the-top christenings and lively St. Patrick's Day festivities.

"Rodeo Girls" 9 p.m. A&E — The ladies reevaluate their lifestyle choices.