The always-tasteful Two and a Half Men (7:30 p.m., CBS/Ch. 2) brings back Tammy (Jamie Pressley), Jake's (Angust T. Jones) much-older girlfriend, for this week's episode.Jake is clearly related to his late Uncle Charlie, because he cheats on Tammy with her 18-year-old daughter, Ashley (Emily Osment). Which doesn't make Ashley's ex-boyfriend, Jerry (Scott Bakula) very happy.For those of you wondering, Pressley is 35; Jones is 19; Osment is 20; and Bakula is 57.For those of you wondering why "Two and a Half Men" is still on - why it's a lock to return next season - the answer is simple. The ratings are good. They're actually better this season than they were last season.Of course, airing after "The Big Bang Theory" doesn't hurt, but the other sitcoms CBS put in this time slot didn't do nearly as well.Elsewhere on TV ...The Big Bang Theory (7 p.m., CBS/Ch. 2): Leonard, Sheldon and Raj compete for tenure.Community (7 p.m., NBC/Ch. 5): Britta and Dean Pelton plan competing dances.American Idol (7 p.m., Fox/Ch. 13): Another contestant faces elimination.AAA baseball (7 p.m., Ch. 14): Tucson Padres at Salt Lake BeesMen's college basketball (7 p.m., ESPN): The NIT final - Baylor vs. IowaProject Runway (7 and 11:02 p.m., Lifetime): Contestants have to create "editorial-worthy" looks.Two and a Half Men (7:30 p.m., CBS/Ch. 2): Jake cheats on his girlfriend with her 18-year-old daughter.Parks and Recreation (7:30 p.m., NBC/Ch. 5): Ron gets sued.Person of Interest (8 p.m., CBS/Ch. 2): Finch infiltrates a tech corporation.Grey's Anatomy (8 p.m., ABC/Ch. 4): April decides to tell her boyfriend she's not actually a virgin.The Office (8 p.m., NBC/Ch. 5): The staff is excited when TV commercials for the documentary begin airing.New Girl (8 p.m., Fox/Ch. 13): Winston and Schmidt try to sabotage Nick and Jess' relationship.Go On (8:30 p.m., NBC/Ch. 5): Ryan's secretary calls him - flirty and drunk.The Mindy Project (8:30 p.m., Fox/Ch. 13): Mindy goes on a date with a minister.Elementary (9 p.m., CBS/Ch. 2): Sherlock and Joan try to prevent a robbery.Scandal (9 p.m., ABC/Ch. 4): Olivia and Jake's relationship heats up; Fitz and Mellie's relationship is ice cold.Anger Management (10:30 p.m., FX): Charlie dates Jennifer's business partner.Archer (11 p.m., FX): Cheryl's brother and his girlfriend are driving her crazy.