When Sugriva saw Rama and Lakshmana approaching Rishyamukha Hill, he was afraid. "They're agents of Vali coming to kill me!"
He sent Hanuman, disguised as a brahmin, to find out what the strangers wanted. "What brings you here?" Hanuman asked. "I inquire on behalf of my king, Sugriva."
Hearing Sugriva's name, Rama rejoiced. "We ourselves are seeking Sugriva!"
"So we are well met!" exclaimed Hanuman. "Get on my back, and I'll take you to him."
Hanuman changed into his monkey form, growing large enough for Rama and Lakshmana to ride on his shoulders, and he carried them to meet Sugriva.
Inspired by: Valmiki's Ramayana
Notes: This is from Book 4: Kishkindha Kanda, sargas 2-3-4. This is the first appearance of Hanuman in Valmiki's Ramayana.