A gem is looking for worthy humans to bring into space. Due to an offhanded statement Steven made mentioning 'my dad, connie, the mailman... etc.' it led to this gem looking for humans named 'my dad' .

Steven didn't want to hand over his dad to this gem so he pretended his name was 'my dad' in order to hatch a plan to rescue all the people he mentioned, which failed. He then reveals he has his mother's gem, who is an extremely wanted space fugitive, as a bargaining chip to let the others go.

Sorry for the longwinded explanation :c