With most companies' third quarters wrapping up about a week ago, earnings season will kick into full swing soon. Of course, the question many investors face in earnings season is, "What companies' earnings reports are worth checking out?"

Two companies' quarterly updates this month that may be worth your time are fast-casual restaurant operator Chipotle Mexican Grill (CMG 0.30%) and social networking platform Twitter (TWTR). The two companies have been on fire this year -- and their stocks have done well.

Here's a close look at these two companies ahead of their earnings releases this month.

Chipotle online order bag

Image source: Chipotle Mexican Grill.

Chipotle

Chipotle is the first of these two companies to report its third-quarter results. The company scheduled its earnings release for Thursday, Oct. 21, after market close. 

2021 has been an eye-opening year for Chipotle shareholders. The company has arguably proved it was more capable than most investors thought -- despite their already high expectations going into the year. New menu items, a successful digital loyalty program, and the rollout of more Chipotlanes (drive-throughs) have been working wonders for the company. As a result, revenue has been skyrocketing. Even more, the company's operating margins have jumped significantly, giving earnings a huge boost. Trailing-12-month revenue and earnings per share are up 27% and 128%, respectively. 

Looking to Q3, management guided for third-quarter comparable restaurant sales, or sales at restaurants in operation for at least 13 months, to grow at a year-over-year rate in the low to mid double digits. 

Twitter

Social networking app Twitter just came off a huge quarter in which advertising spend rebounded from a pandemic-stricken period in the year-ago quarter when many advertisers paused or reduced their ad spend. Twitter's second-quarter revenue soared 74% year over year. 

While revenue growth is expected to slow in Q3 as the company faces a much tougher year-ago comparison, management's guidance for revenue between $1.22 billion and $1.3 billion during the period still represents a big jump over its $936 million of revenue in the year-ago period. 

Of course, investors will want to keep an eye on Twitter's user trends as well. Its monetizable daily active users grew 11% year over year in Q3. As the lifeblood of the company's business, investors should look for similarly strong year-over-year growth in the key metric in Q3.

Twitter reports its third-quarter results after market close on Tue., Oct. 26.