Who is Betty? (S06E20)

S06E01 Fixing Up the Fraternity House S06E02 The Man Without a Family S06E03 Treasurer's Report S06E04 The Boys Land in Jail S06E05 Mystery Shopper S06E06 Ricky's Big Night S06E07 Free Flowers S06E08 Ozzie's Triple Banana Surprise S06E09 Fourteen Mile Hike S06E10 Tuti-Fruiti Ice-Cream S06E11 The Christmas Tree Lot S06E12 Ricky Goes on TV S06E13 The Trophy S06E14 The Road Race S06E15 David and the Stewardess S06E16 The Picture in Rick's Notebook S06E17 Harriet's Dancing Partner S06E18 The Safe S06E19 David and the Men's Club S06E20 Who is Betty? S06E21 The Old Band Pavilion S06E22 The Practical Joker S06E23 Scavenger Hunt S06E24 The Dating System S06E25 The Closed Circuit S06E26 The Top Gun S06E27 The Record Trout S06E28 The Bachelor S06E29 Code of Honor S06E30 Ricky is Micky S06E31 Rick's Chemistry Grade S06E32 The Magic of Three S06E33 The International Set S06E34 Ozzie and the Bridge Group S06E35 A Cruise for Harriet