Will a fast ball work on Entei on Pokemon HeartGold

if you are very lucky it may...but i really doubt it..the best way to catch it is with a gengar/snorlax or any Pokemon who can learn block, mean look, or have the special ability to unable the wild Pokemon to escape...after that, ur best shot is to make it fall asleep, poidon, par, or make it confuse..(not recommended)

after the status problem, hurt it until its hp is on red..and then try with ultraballs if its day, and dusk ball if its night..

u should have at least 20 for the worst case..

REMEMBER TO SAVE BEFORE TRYING TO CATCH IT! ENTEI HAS ROAR!

so it will take you a while until u can catch it..believe me, i tried so many times..and after a day and half of trying i got him today..