"Sandcastles in the Sand" is the 16th episode in the third season of the television series How I Met Your Mother and 60th overall.
At MacLaren's, Robin announces that her former boyfriend, Simon (James Van Der Beek), will be meeting her there later.
Robin describes their break-up: after she loaded his band's equipment into their van after a performance, he dumped her.
When Robin attempts to defend herself, the group discusses how being around someone from your past can cause you to revert to the person you were when you knew them, a phenomenon Marshall dubs "revertigo".
Mirroring their original break-up, Simon once again has Robin assist him with loading his van, then dumps her.
Robin drinks alone at MacLaren's until Barney arrives, complaining that he has yet to find a copy of her video.