what a great question.
watching a friends mother sat with her feet up, legs through the wooden bits of a dining room chair, unable to move them because the 2 yrs old was sat on her lap. shoes off, soft feet showing, when my friends brothers descended on them and tickled her for about 2 minutes.
she could be a real bitch, but was helpless and laughed and laughed and squirmed and laughed louder until the laughter turned silent.
her face was one of disbelief at first, she couldn't do the annoyed thing cos there were 7 of us in the lounge, and pretty soon into the tickling her face was that look which Amanda gets, when she could be in front of a football crowd but she is that place of her own called hysteria and is unaware orf everything but her own laughter, head thrown back mouth wide open, laughing and taking huge gulps of air. .
this was over 20 years ago and she was in her mid 30s then.