Historical clue formulations

• Part of some McDonald's restaurants — 2020-01-10
• What the keys are to a pianist? — 2017-04-19
• Feature of many a McDonald's — 2014-09-20
• Pediatrician's amenity, often — 2012-10-20
• Romper room — 2006-12-29
• Recreation center — 2005-04-17