In case you hadn't noticed, the characters in Cowboy Bebop map nicely onto those in Captain Future, though it's not a bijective mapping. (And by mapping I don't mean the characters are similiar; I mean they're analogous.)
The Captain <-> Spike Spiegel
Greg, Otho <-> Jet Black
Professor Simon (Ken Scott?) <-> Edward
Ul Quorn <-> Vicious
Joan Randall <-> Faye Valentine
Yiek, Oak <-> Ein
Which leaves out Ezra Gurney, a fairly major character. The best I can come up with is Alfredo ("Punch") from Big Shot. He dons a moustache, he's getting quite some screen time, and he fills the crew in on the baddies.