They didn't. What game do you believe it happened in?
How did someone get to move 2 times in a row 2 times against me

i cant remember but unless there is lag i swear 2 times i saw this guy mvoe 2 times in succession but that isnt a game is it the guy actually told me that it is allowed in a certain blitz type game but maybe he misunderstood me im not sure

No, it's not possible. Castling moves both the rook and king at the same time but I'm guessing that's probably not what you saw
i cant remember but unless there is lag i swear 2 times i saw this guy mvoe 2 times in succession but that isnt a game is it the guy actually told me that it is allowed in a certain blitz type game but maybe he misunderstood me im not sure
You only have a few games played three days ago on 21 oct. You can look through the games in the game archive to review the games again. There should not be a time when your opponent plays two moves in succession at all. Castling, promotion and en passant are some instances where two things are being made at once. Castling moves the king and the rook on the same turn; promotion gets rid of the promoting pawn and a new piece emerges; en passant moves the capturing pawn one square diagonally forward whilst capturing an opposing pawn.

Literally just happened to me. Is this a bug? My last move was undone, and my opponent got two moves in a row.

Literally just happened to me. Is this a bug? My last move was undone, and my opponent got two moves in a row.
Game link? That just doesn't happen.

If you mean this game, https://www.chess.com/live/game/6448059161
You moved Nc3 and moved it back to b1 the very next move. If you have premoves on, it probably was an accidental premove.

My opponent got 2 moves in a row. It's disappointing.
Do you have a link to the game and which move you think it happened on? It's possible you accidentally premoved and it just looked like the opponent moved twice.
How did someone get to move 2 times in a row against me in blitz mode isnt that cheating? thank you.