There are many synonyms for the phrase "become pally with," which means to become friendly with someone. One synonym could be "befriend," which means to make someone a friend. Another synonym could be "bond," which means to create a strong connection with someone. Other synonyms include "associate with," "socialize with," and "hang out with." It is important to note that while these synonyms all describe a similar type of relationship, they may have slightly different connotations. For example, "associate with" may be more formal than "hang out with." Overall, it's important to choose the synonym that best fits the tone and context of the situation.