Examples:

• Maja and Amanda were as thick as thieves.
• I mean, another lifetime, you and me, we... could have been thick as thieves, you know?
• And-and you, you used to tell me everything, too, and now you and my brother are as thick as thieves.
• You two are as thick as thieves, aren't you?
• Interesting fact... the phrase "thick as thieves" was coined in... Not now, Brick.
• You two are thick as thieves, now.
• I say by the end of the evening you two will be thick as thieves.
• Yeah, thick as thieves, I reckon.
• The executive and legislative powers are thick as thieves, dodging the truth, like in the famous Vermeer painting, in view of the onlookers, European citizens.
• The cop let you go. - Yeah, we know each other. We're thick as thieves.