Panda!Hiro is a very small panda as well. He's not expected to grow larger than a twelve year old child. And he follows Tadashi to all of his classes eventually, the teachers and students all think it's the cutest thing in the world. Also Hiro eventually thinks that he's a human, and Tadashi's his real mom, but Tadashi doesn't notice this.
Tadashi comes home to see Panda!Hiro eating hot wings and stares for a few minutes, then yells, "AUNT CASS! YOU OF ALL PEOPLE SHOULD KNOW THAT HIRO'S ON A SPECIAL DIET!"
Tadashi does, however, have a fondness for dressing Hiro up in little outfits. He caught Hiro trying to put on one of his shirts once (very unsuccessfully), and the idea was too cute to pass up.
And in Aunt Cass’ defense, she didn’t actually feed Hiro hot wings. They were supposed to be for Tadashi, but she made the mistake of turning her back for more than three seconds, and Hiro got into them. They’re both just shocked that an animal that exclusively eats bamboo is willing to even try hot wings in the first place.
Still, hot wings are not good for pandas, and Tadashi makes sure that Hiro doesn’t actually consume any of the food. Because that’s what his job is as Hiro’s keeper XD