Tokis-Phoenix
^_^
I suggest a small iridescent shark or two. I know, I know, they can get big. They won't as long as you don't put them in a bigger tank. I have some, and I know they are pleasant, funny, and non aggressive fish who have dealt pleasantly with my own platies and swordtails.
Irredescent sharks grow to 4ft long, even if its only an inch long when you buy it, a 4gallon is still waaay too small for an irredescent shark, look at the pics if you don't believe me;
http/www.planetcatfish.com/catelog/panga...gasiu/172_F.PHP
I don't think there are any shark types that will go in a tank under 25gals.
karen4kevin, if you upgrade to a 15gal that would be alot better and drastically open up alot of stocking optunitys- i'd still do a fishless cycle though whatever tank you get . 1male and 4female platys would be good in a 15gal, you could also get some corys like 4-5 albino/bronze or pepppered corys if you go for sand or fine rounded gravel substrate as well, and maybe a tetra species or two? What sort of fish are you into ?