Yamcha Knows the Genki-Dama
This is not quite a “dub mistake” since the confusion is not because of anything FUNimation did or changed; it is actually due to fans not hearing correctly!
In episode 17 of Dragon Ball Z (episode 11 in FUNimation’s original edited English dub), several of the Z-Warriors use a special room in God’s palace to essentially “time travel” and fight a pair of “Illusion Saiyans”, all in preparation for the upcoming battle against Nappa & Vegeta. During this fight, Yamcha uses one of his new trademark techniques, the Sōki-Dan (“Spinning Ki Bullet,” first shown in the fight against Shen/God at the 23rd Tenka’ichi Budōkai).
In FUNimation’s original dub, we hear Yamcha speak the name of the attack, and many fans were unsure of what was actually being said. If you turn on the closed-captioning, you will see that the script calls for Yamcha to say “Spirit Ball” as he forms the attack. Many fans, having seen the remainder of the first season and being familiar with the attack from Goku, thought Yamcha was actually saying “Spirit Bomb” (which is their name adaptation of the Genki-Dama, the ball of life energy he would use against Vegeta, Freeza, and Majin Boo).
Needless to say, Yamcha does not know how to perform the Genki-Dama. Whether or not he could possibly learn it from North Kaiō or Goku and then use it is never explored, but that certainly doesn’t stop fans from asking this question on a daily basis…!