Grandpa

In the twelth episode of the eiighth season, The_Space_Probe_Disintegration, Grandpa is an elderly Hindu worshipper who is unfortunate enough to have a minor parking accident in the temple car park, which dents Raj K's car. Raj, worried about the fate of a space probe he collaborated in, who has just been explaining at length to Howard about the Hindu principles of the interconnectedness of all things and how a true Hindu should remain stoic in the face of adversity, loses it. The unfortunate Grandpa receives the full force of Raj's wrath, until Howard calms him down by advising him that the Pluto probe has now arrived safely and is transmitting pictures. he demonstrates this by waving his phone, carrying the first Pluto images, in Raj's face.

Suddenly Raj is the personification of Hindu respect to one's elders, and gives the bemused Grandpa a bow and a folded-hands Namaste!.

It is not clear if Grandpa is an actual relative, or if Raj is using a general honorific to an elderly man.