Perfect Rhymes:
* hippopotamus (more formal, but technically accurate)
* pippo (less common, but playful)
Near Rhymes:
* dipper
* chipper
* nipper
* ripper
* sipper
* slipper
Eye Rhymes (look the same but sound different):
* hippo (can be used to create a humorous effect)
You can also consider using words that rhyme with syllables within "hippo", like "po" in "go" or "hop" in "flop".
Choose the rhyme that best suits your poem!