well here's the thing. I have tiger barbs, neons, red tail shark, harlequin rasboars, and a couple algae eaters in my 55 gallon. i also have 2 sunset platys. but i have never ever had guppies because of my more aggressive fish. and these two baby fish showed up in my tank one day. i thought that my two sunset platys had babies or something. until they got older and never got the orange color to them. they are kinda see through yellow, as you can see. So where did these little guys come from?!?!
It's possible they somehow managed to get into your bag at the pet store. One way I could see this happening is if the last customer the employee helped bought some guppies and some fry got left behind in the net or holder.
well they have been in there since they were babies and now they are full grown! so i guess this just goes to show that you can have semi-aggressive fish with guppies because they don't bother anyone at all! weird.