a giant galaxy interacting with its satellites is common. a satellite's gravity could attract one of the primary's spiral arms, or the secondary satellite's path could coincide with the position of the primary satellite's and so would dive into the primary galaxy (the sagittarius dwarf elliptical galaxy into the milky way being an example of the latter). that can possibly trigger a small amount of star formation. such orphaned clusters of stars were sometimes referred to as "blue blobs" before they were recognized as stars.