List (Pokémon~Pokémon similar to)Mew ~ Staryu Kadabra ~ Gastly Paras ~ Staryu Parasect ~ Staryu Starmie ~ Staryu Raticate ~ Rattata Magneton ~ Gastly Krabby ~ Mr. Mime Vulpix ~ Graveler Ninetales ~ Graveler Geodude ~ Graveler Metapod ~ Gastly Mewtwo ~ Staryu Krabby ~ Mr. Mime Kingler ~ Mr. Mime Alakazam ~ Gastly Magnemite ~ Gastly
ExplanationAlthough there are 151 Pokémon, there are only 38 'base cries'. Individual Pokémon cries have their own 'pitch' and 'length' cries which allow two Pokémon with the same base cries to sound different.
When the player sends out a Pokémon with low HP and the red bar sound effect plays, it will effectively cause the game to play the cry with pitch $00 value instead of the normal pitch; and if this cry is similar to the expected data of another Pokémon, it may sound like that Pokémon. For example, Kadabra's cry data is base $1C, pitch $A8, length $C0. Through red-bar manipulation, sending out Kadabra will effectively play base $1C, pitch $00, length $C0; which is the same as Gastly's cry data (base $1C, pitch $00, length $80) but with a longer length value.
If the player uses the GameShark code 0100F1C0 for Red/Blue/Yellow (which modifies the pitch of a Pokémon cry to 0), then they can make a Pokémon's cry sound like the low HP equivalent without actually needing low HP.