The term "regular fellow" can be replaced by several synonyms depending on the context. For example, "ordinary guy" can be used when referring to a person who is average in every way. "Average Joe" and "common man" are also suitable synonyms that describe a regular guy. One can use "everyday fellow" or "run-of-the-mill type" if they want to imply that this individual is unremarkable or ordinary. "Simple man" can also be used to describe the regular fellow who prefers a straightforward and uncomplicated existence. In summary, there are many fitting synonyms that can be used to describe a "regular fellow".