36th President: Lyndon B Johnson, 1963 

Mash = 36 (Johnson was the 36th president)

John's son = Johnson

NOTE: The John is another name for a toilet.

Pyjama = 963 = 1963 became president

Leaned on = Lyndon 

His dad ate mash (36) as he sat on the john, while the john's son (Johnson) was used by the pyjama boy (963 = 1963).

Connect Johnson to Lyndon

Sometimes the john's son (Johnson) just has to be leaned on (Lyndon) when you're not feeling well.

NOTE: The way Mammoth Memory remembers Lyndon is to think Lyndon – leaned on.