The phrase "do a lot of silly things" can be replaced with a variety of synonyms to express the same concept in different ways. Some synonyms that may be used include "act foolishly," "behave childishly," "indulge in tomfoolery," "engage in absurd antics," "play the fool," "act hilariously," "behave comically," or "engage in nonsense." Each of these synonyms conveys a slightly different nuance of meaning, but all communicate the idea of engaging in behaviors that are not serious or sensible. Whether the phrase is used in a lighthearted or critical way, these synonyms can help to add variety and interest to speech or writing.