Peter has to try really, really hard not to smile at that one. He clenches his jaw and tries to clear his mind of thoughts entirely, but he knows without a doubt now:

It's time for the big guns.

Tony knows his weakness. It was his fault for demonstrating to Tony exactly what he found funny to begin with. It was probably also his fault for calling him dad, too. Peter's sure that as soon as you become a father (honorary or no), it allows you to tap into unladen, potent dad joke energy, and Tony likely had a lot stored up since he was 47 now and Peter was technically his first kid.

"Anyway, if we're not actually drinking tonight, can I ask you to do me a favor?"