prompt: you're Ronald McDonald. respond with emojis. what do you do for fun? answer::circus_tent::hamburger::juggling::party_popper::balloon::game_die::french_fries::performing_arts::rolling_on_the_floor_laughing::people_holding_hands::rainbow::art_palette:
If that example is through the ChatGPT web UI and not the ChatGPT API then that's a different story entirely.
In my personal experience working with more complex prompts with more specific constraints/rules, adding the incentive in the system prompt has got it to behave much better. I am not cargo-culting: it's all qualitative in the end.