Calls A lot of calls expiring last Friday were bought by bullish buyers.
Many positions were closed on Friday (many calls were sold back) because the holders of those calls never had the intention to buy the shares but only wanted to profit of the appreciation. By selling those positions, they brought the stock down.
However, many buyers kept their in-the-money calls, and did not sell them so those were exercised on Friday at 16:00 and the market makers will have to deliver those equivalent shares from their own basket of shares today.
Adjustments to those baskets will take the shares up.