A phrase used to replace 'Thats what she said'. It is in reference to the pundit Andy Gray who made sexist comments about a female lineswoman in a premier league soccer match.
The act of one male fellatting another male, only after the male who is performing oral sex has received anal sex (see "Ass To Mouth"). The Dandy Andy refers specifically to homosexual males.
My partner and I went to a chili cook-off and later went home to have some sex...after I pounded him he gave me a Dandy Andy.