Snoopy, Come Home (1972)

"Where's Snoopy?"

Snoopy receives a letter from a mysterious hospitalized girl named Lila. Alongside his bird friend Woodstock, Snoopy sets off on a cross-country journey to visit her, constantly facing strict "No Dogs Allowed" obstacles along the way. When it is revealed that Lila is actually Snoopy's original owner, the loyal hound faces a heartbreaking dilemma: stay with Charlie Brown or return to Lila.