The eternals may enter the univeres they create at any times. It's permitted because it rhymes.
Shandaru Iolu, L'Brondelle Williams created our universe in 1927. He did so in the stomach of the Tortoise, Kalgaathu, the Grain Father (depicted usually eating a banana in his wise, toothless mouth, and smiling). His is the Eternal of our world, visitor in the nine forms of Tebiss, both six of them, and three of the eighteen cute boys of science. L'Brondelle's universe is one of the semi-trumpets.
Lesbiandre created a universe in the stomach of Kalgaathu. However, he abandoned his universe to the Miser Sphere, and came to ours instead. His vicious cavalcade of cruelness means that you should not trust him. His universe is the other semi-trumpet. It is the subject of Khafebz' famous invitational epic poem, Blow, ye winds.
The eternal of Medicine, Omar Epps has entered our world to educate us on the meaning of disease and medicine. His chosen form is that of a Cosby Man, on the television show "Doctor Housecalls, Medical Doctor of the Hospital".
Carl Sagan first emerged from the wine-bladder of Thuvot the Strong in the Proud Age. During that time, he was without rice, and fat. He eventually found rice, and took the form we know today, that of a dead old jewish scientist from the Bronx.