The Sirians are reputed to have a connection to Dolphins, which they have supposedly genetically engineered and are genetically related to. This is entirely false, although Dolphins are as intelligent as dogs or horses or pigs, and as such are sentient animals deserving of consideration. In fact, as souls may incarnate temporarily into such animals, they should be considered to have this possibility. When you see a Dolphin, you may be seeing your brethren, and just so your faithful dog. A rare chance, but possible.
So why did this rumor start? Various human groups, wishing to be poetic and special in some way, have invented romantic notions about themselves and various animal groups. By such means, human groups have claimed relationships to high flying birds, sleek jungle cats, and athletic and playful sea creatures such as Dolphins. This is all a way to make the day go faster, and be more playful and bright. Fantasy.