The Catch 'Em Mode music in Blue Field is based on the music from the Japanese opening of the Pokémon Anime.
Mew can appear as a catchable Pokémon in Indigo Plateau once the player has completed the Mewtwo bonus stage twice (it then has a 1/16 chance of being encountered when all three GET lights are lit). However, it can't actually be caught by normal means, because a special routine increments a counter in a RAM address whenever Mew is hit, and each of the 4 steps in the "catch!" sequence requires the player to hit Mew 256 times (for a total of 1024 hits, basically impossible within a two minute timeframe). Mew's Pokédex entry will be unlocked when it is encountered instead of when it is obtained.