adṛṣṭa-pūrvaḿ hṛṣito 'smi dṛṣṭvā
bhayena ca pravyathitaḿ mano me
tad eva me darśaya deva rūpaḿ
prasīda deveśa jagan-nivāsa
Arjuna therefore is asking Kṛṣṇa to show His Nārāyaṇa form, because He can assume any form. This universal form is material and temporary, as the material world is temporary. But in the Vaikuṇṭha planets He has His transcendental form with four hands as Nārāyaṇa. There are innumerable planets in the spiritual sky, and in each of them Kṛṣṇa is present by His plenary manifestations of different names. Thus Arjuna desired to see one of the forms manifest in the Vaikuṇṭha planets. Of course in each Vaikuṇṭha planet the form of Nārāyaṇa is four-handed, but the four hands hold different arrangements of symbols — the conchshell, mace, lotus and disc. According to the different hands these four things are held in, the Nārāyaṇas are variously named. All of these forms are one with Kṛṣṇa; therefore Arjuna requests to see His four-handed feature.
Bhagavad-gītā As It Is 11.45