Show me your favourite on-screen in-jokey 'Easter Egg'!

Here's one of mine, a real deep cut:

Robert Redford opening his fridge in Captain America: The Winter Soldier to reveal a bottle of Newman's Own in honour of his Butch Cassidy co-star, Paul "All profits to charity" Newman

Another fun Marvel Easter Egg is Arrested Development veterans @Russo_Brothers putting the Bluth Family stair car in the Berlin airport fight in Captain America: Civil War

Side note: I remember resisting saying 'I'm afraid I just blue myself' out-loud in the cinema when I spotted this in Avengers: Infinity War