During interphase, the major differences between animal and plant cells are overall shape, appearance of vacuole(s), and location of the nucleus. Because plant cells are enclosed in a fibrous cell wall, they tend to be square or rectangular in shape with angular corners, whereas animal cells can take on a wide variety of shapes, but almost never have square corners. Plant cells usually have a much larger vacuole than animal cells, and consequently the nucleus and other organelles of a plant cell are usually pushed to one side, while the nucleus of the animal cell will be close to the center of the cell.
During mitosis, the animal cell will have visible centrioles, where the plant cell will not. In thin section slides, you will also see that the onion cells are all dividing along the same axis, while in the whitefish embryos the plane of division appears to be random.
During cytokinesis, the animal cell completes division by pinching in in the center, while plants cannot do this and instead build a cell wall across to complete the cell division.