Jake's undercover FBI operation ends in a successful sting, until he learns one mobster has gotten away. As Jake enlists Charles' help to track him down, Holt tests the squad's patience with practice drills.

So, "Undercover" picks up as Jake is arresting the majority of the mob organization and returns to work - where only three big things happened in the six months he was away (Terry with a lisp, Amy and Charles in the same outfit & the banning of headphones). His return does undercut a bit of the importance the FBI job meant to Jake. It was a promotion he was excited about and we didn't get the opportunity to see any of it. But Jake does often work better as a character when he is around his fellow detectives. His undercover work is never really about the criminal organization he's trying to take down. They are basically mob stereotypes - although the bit about singing Billy Joel together did work. The story is never really about them. I do wish they gave Jenny Slate more to do but they also left her in play for a possible return appearance later which I wouldn't not want to see. The story truly is about Jake trying to overcompensate yet again at work as a way to deal with his feelings towards Amy. It's a consistent character beat for sure. And yet, him accepting that there are things he cannot change at the very end leaves me hopeful that the show won't go to that well ever again.
The show even gets to have some meaningful work with the Gina and Charles story. They simply play it as not being a big deal while Jake was away but a huge one since he's back - which is an explanation I can deal with. It helps immensely that they slept together again at episode's end. It makes the experience much more fresh in the narrative. But also has the hint of: Is there something here between these two? It didn't happen twice by accident. That could potential be interesting to see how the show explores that dynamic - and if Charles will be able to keep the secret.
But the true comedic highlight of the premiere comes from Terry, Amy and Rosa doing practice drills for the Captain. Terry Crews stole every scene he was in. It helps that he got to play an angry prostitute, a confused old lady, an unattended backpack and a 7-year-old boy all of which are hilarious when seen through his stature. But change is coming to the police department soon. Holt has no idea what to expect and is making sure his precinct is ready for anything. Sure, it's another case where Holt's words and logic can be used against him. But dang, it was a lot of fun - especially when Terry, Amy and Rosa were in the bounce house and then trying to escape as it deflated.
Some more thoughts:
- Charles' frustration with Derek - the guy Jake did some jobs with for the mob - was also quite great. His thoughts disassociated with his body!
- Holt was constantly smiling before all this uncertainty going on above him in case you couldn't tell.
- The car door continually getting locked then unlocked which leads to frustration from Charles was great. And yet, it was also similar to a sketch that aired on Key & Peele just a few days ago.
- Gina is convinced Charles will tell Jake their secret and thusly braces herself with the pending fall from the social ladder. Not the funniest bit from the premiere although the bluntness of the naked mole rat was enjoyable.
- Gina to Charles: "Every time you talk I hear the sound when Pac Man dies."
- Terry reading Holt's script: "I am feeling trepidation at the prospect of a parentless existence." Holt's response: "Those words were lifted verbatim from my boyhood journey."