I am sorry to say I am tearing up laughing at your tale. The bird was okay and likely learned from his experience, though.
Reminds me of when I was a kid and blue tits nested in our mural mailbox. My brother and I, being kids, would open the mailbox door (inside the house) to peek at the babies. Anyway. Have you ever tried to catch an irate and terrified blue tit mama while she's frantically flying in a 2x2m hallway, so you can put her back in a large rectangular hole in the wall, this at one in the morning, while praying your mother won't wake up? Because I have.
even inside the apartment in some 3D printed bird feeders
Oh boy, you like to live dangerously. How did that go?
I'm doing the same (outside the window) with bird seed, so I'll sometimes enter my kitchen and find pigeons / collared doves staring at me. But they just stare and stare and then fly away. No war cries.
Blue tits are always the loudest, most annoyed birbs when I'm out. They'll alert constantly. Which makes them a lot easier to photograph.
Nice shot! The framing is neat.
Also what is looking at? He certainly seems to disapprove of it.