Mr. Ha Ha's Hog Dog Hacienda is a fictitious children's restaurant based in Miami, Florida. It is named for its mascot, a clown called Mr. Ha Ha, who also hosts birthday parties at the restaurant and interacts with guests. It made its first and only appearance in A Piece of Cake, and was where Rose Nylund took her friend Dorothy Zbornak for her birthday in 1987, to the latter's chagrin.
The scene is done as a flashback about the girls reflecting on birthdays past.
Rose took Dorothy and Blanche to the restaurant after seeing it on TV and listening to Dorothy complain about her birthdays being dull (Sophia was still at Shady Pines). It's clear that Dorothy doesn't enjoy the place or Rose's reason for it, Rose gets upset, Dorothy and Blanche pretend to enjoy it for Rose. However Rose told the management that it was Dorothy's birthday. When Dorothy hears her name called, she attacks Rose, Mr. Ha Ha gets her on-stage, Dorothy is forced also to walk around in a hat and is mocked by Mr. Ha Ha as a cranky old woman. She goes to pie him with her small Birthday Sundae but he warns her that he could sue and that it's an immature thing to do, however, Bobby Spina, a boy whose birthday was the same day, pies Mr. Ha Ha and said Happy Birthday to Dorothy who is clearly touched by this boy's action.